JAIST Repository
https://dspace.jaist.ac.jp/

Title

Pt/Ir ナノ粒子を修飾したデュアル機能剝離アセチレンブラ
ックのリチウム空気電池への応用

Author(s)周, 立航

CitationIssue Date

2024-03

Type

Thesis or Dissertation

Text version

ETD

URL

http://hdl.handle.net/10119/19078

RightsDescription

supervisor: 松見 紀佳, 先端科学技術研究科, 博士

Japan Advanced Institute of Science and Technology

博士論文

Bifunctional Pt/Ir nano-particles decoratedfunctionalized acetylene black andits application in Li-air batteries
Pt/Ir ナノ粒子を修飾したデュアル機能剝離アセチ
レンブラックのリチウム空気電池への応用

ZHOU Lihang
主任研究指導教員 松見 紀佳

北陸先端科学技術大学院大学 金沢大学
融合科学共同専攻
融合科学

令和6年3月Abstract
Bifunctional Pt/Ir nano-particles decorated functionalized acetylene black andits application in Li-air batteries(Pt/Ir ナノ粒子を修飾したデュアル機能剝離アセチレンブラックのリチウム空気電池への応用)
Li-air batteries offer superior energy density compared to traditional Li-ion batteries , aligning with the global
shift toward sustainable electric vehicles. The cathodic efficiency crucially hinges on the oxygen reduction
reaction (ORR), for which platinum supported on carbon (Pt/C) has been a prevalent catalyst. However, thechallenge in Li-air batteries lies in the simultaneous requirement for oxygen evolution reaction (OER) alongside
ORR. This predicament has spurred investigations into amalgamating Pt with high OER activity metals like Ir,
Co, and Fe. Despite their promising performance, the stability and potential leaching of these catalysts remain
significant challenges [1].
This study exploits a carbon substrate demonstrating strong metal substrate interaction (SMSI) for heightenedelectrocatalytic durability. Building upon prior work [2], a novel functionalized acetylene black (Pt-FAB) was
introduced, exhibiting remarkable catalytic activity due to efficient interfacial interactions with nanoparticles andelectrolyte. The current study augments OER activity by incorporating Ir into the Pt-FAB catalyst. This unique
Pt-Ir/FAB combination is anticipated to offer both high activity and durability, owing to efficient interfacial
properties [3].
Acetylene Black (AB) is treated with a mixed strong acids to improve dispersion in water or organic solutions,enabling the formation of a catalyst with multiple functions. ORR and OER experiments are performed in an
organic electrolyte, using TEGDME with 0.1 M LiFSI or LiTFSI. The next step involves constructing a Li-air
battery, where a cathode slurry with active materials is coated on a carbon cloth. The electrolyte, consisting of
0.1 M LiI and 1 M LiTFSI in TEGDME, is used, and the battery operates under a 99.9% oxygen atmosphere at
0.1 MPa. The capacity is limited to 1000 mAh/gPt-Ir at charge-discharge rates of 125 mA/g and 250 mA/g toevaluate the material's long cycle life.
Acetylene Black (AB) treated with mixed strong acids enhances dispersion, which is crucial for forming acatalyst with controlled size and distribution. This work introduces a pioneering bimetallic Pt-Ir catalyst on
functionalized acetylene black (FAB) for Li-air batteries. FAB, modified with -COOH functional groups, serves
as a stable substrate for metal nanoparticle deposition. X-ray photoelectron spectroscopy (XPS) confirms
successful Pt0 and Ir4+ deposition on FAB. Electrochemical measurements reveal satistactory activities in ORR
and OER, sustaining over 250 cycles in organic electrolytes. Cyclic voltammetry underscores its potential for Liair battery. FAB180-Pt/Ir 1:1 with a 1000 mAh/g charge-discharge capacity maintained constant performanceover 70 cycles, showcasing outstanding OER and ORR activity.
Bibliography< References >[1] Girishkumar, G., McCloskey, B., Luntz, A. C., Swanson, S., & Wilcke, W. The Journal of Physical Chemistry
Letters, 1(14), 2193-2203 (2010).
[2] Badam, R., Vedarajan, R., & Matsumi, N. Chemical Communications, 51(48), 9841-9844 (2015).
[3] da Silva, G. C., Fernandes, M. R., Ticianelli, E. A., ACS Catal, 8, 2081e92 (2018).
Keywords: Oxygen reduction reaction, Oxygen evolution reaction, Dual electrocatalysts, Li air batteries,
Rechargeable battery

Acknowledgements
Firstly, in completing this dissertation, I express my gratitude to all members of Matsumi Lab. I
am especially thankful to Professor Matsumi for his invaluable guidance as my supervisor, offeringboth expertise and encouragement throughout this work. His patience, motivation, and extensive
knowledge were instrumental in both my research and thesis writing.
I extend my appreciation to Professor Badam, an assistant professor, for the support and advice
provided during laboratory experiments.
I would also like to thank Professors HORITA Susumu (JAIST), TAIMA Tetsuya (Kanazawa
University), MIZUNO Motohiro (Kanazawa University), and Dr. HIGASHIMINE Koichi (JAIST)
for their substantial contributions to my research.
Furthermore, I am sincerely grateful to everyone who supported me during my doctoral studies at
JAIST. My thanks go to the members of Matsumi Lab and all professors who shared their knowledge
during lectures and research.
I am deeply indebted to my family and friends for their support and extend my best wishes to all.
Lastly, I express my gratitude to JAIST. The doctoral period has been a profoundly significant
experience in my life.

ZHOU Lihang
January 2024

1

2023

Bifunctional Pt/Ir nano-particles decoratedfunctionalized acetylene black and its application in Li-air batteries

ZHOU LIHANG (MATSUMI LAB.)Contents
1.

Chapter 1 ....................................................................................................................................... 1
1.1.

Background .......................................................................................................................... 1

1.2.

Secondary Batteries and Lithium Air Batteries ............................................................... 3

1.3.

Electrocatalyst for Cathode .............................................................................................. 11

1.3.1.

Oxygen Reduction Reaction (ORR) ................................................................................. 11

1.3.1.1.

Mechanism of ORR ....................................................................................................... 11

1.3.1.2.

Mechanism of ORR on Carbon Materials .................................................................. 12

1.3.1.3.

ORR on Carbon Nanotubes ......................................................................................... 13

1.3.1.4.

ORR on Heteroatom Doped Carbon Atoms ............................................................... 14

1.3.1.5.

ORR on Pretreated Carbon Surface ........................................................................... 14

1.3.1.6.

ORR Activity on Precious Metals ................................................................................ 14

1.3.1.7.

Fuel-cell and Li-air Battery .......................................................................................... 16

1.3.2.

Oxygen Evolution Reaction (OER) .................................................................................. 19

1.3.2.1.

Mechanism of OER ....................................................................................................... 19

1.3.2.2.

Mechanism of OER on Carbon Materials .................................................................. 21

1.3.2.3.

OER Activity on Metals ................................................................................................ 21

1.3.2.4.

Li-Air Battery Using Metals ......................................................................................... 23

1.3.3.

Application of Bi-functional Catalyst and Li-Air Battery Design................................. 24

1.4.

Introduction on Carbon-metal Based ORR and OER Catalyst .................................... 25

1.5.

Facet Controlled Catalysis ................................................................................................ 26

1.6.

Enhancement of Catalytic Activity of These Alloys ....................................................... 27

1.7.

Synthesis of Core Shell Nanoparticles: ............................................................................ 28

1.8.

Design and Utilization of FAB Based Catalyst................................................................ 29

1.9.

Important Evaluation Methods and Basic Principles .................................................... 31

1.10.

Conclusion and Outlook about This Research ................................................................ 34

References ............................................................................................................................................ 35
2.

Chapter 2 ..................................................................................................................................... 37
2.1.

Abstract .............................................................................................................................. 37

2.2.

Introduction ....................................................................................................................... 38

2.3.

Materials Synthesis ............................................................................................................ 40

2.3.1.

AB Carbon ......................................................................................................................... 43

2.3.2.

FAB carbon and preparation ........................................................................................... 44

2.3.3.

Pt Carbon ........................................................................................................................... 46

2.3.4.

Pt/Ir Carbon ....................................................................................................................... 47

2.4.

Analysis and Discussion .................................................................................................... 50
12.4.1.

SEM-SED ........................................................................................................................... 50

2.4.2.

TGA .................................................................................................................................... 53

2.4.3.

TEM .................................................................................................................................... 54

2.4.4.

XPS...................................................................................................................................... 60

2.5.

Conclusion .......................................................................................................................... 76

References ............................................................................................................................................ 77
3.

Chapter 3 ..................................................................................................................................... 78
3.1.

Abstract .............................................................................................................................. 78

3.2.

Introduction ....................................................................................................................... 79

3.3.

Materials and Experimental ............................................................................................. 82

3.3.1.

Catalyst ............................................................................................................................... 82

3.3.2.

Electrochemical Detection ................................................................................................ 83

3.3.3.

Air-Battery ......................................................................................................................... 83

3.4.

Analysis and Discussion .................................................................................................... 86

3.4.1.

LSV ..................................................................................................................................... 87

3.4.2.

CV ....................................................................................................................................... 90

3.4.3.

Charge-Discharge .............................................................................................................. 93

3.5.

Conclusion .......................................................................................................................... 99

References .......................................................................................................................................... 100
4.

Chapter 4 ................................................................................................................................... 101
4.1.

Conclusion of This Work ................................................................................................ 101

4.2.

Future Scope of This Work............................................................................................. 106

21. Chapter 1
Introduction

1.1.

Background

Recently, global warming and alternative energy are becoming the exploratory aspects in thescientific world. Since the 1800s, as a result of the Industrial Revolution, fossil energy was amajor source of power. With consumption of fossil energy, global CO2 (Carbon Dioxide)
emissions had grown up quickly (Fig. 1-1). At the same time, the concentration of CO2 in theatmosphere under continuous monitoring has reached an alarming level (Fig. 1-2). [1]How to control and reduce Global Warming is a challenge around the world. For this reason,
we need to choose alternative energy sources. In the near future, wind power and solar power
will be typical resources where from we would derive the electricity.
Since 1800s, the electric battery is an important source of electric power. In a narrow sense, abattery is a device that converts its stored chemical energy into electrical energy; battery could
become a device that converts "pre-stored" energy into electrical energy for external use.
Batteries are key to deal the problems in smooth and efficient use of stored energy for a numberof cycles. Then, clean energy system will be set up and will work in a more desirable manner.

Fig. 1-1 Global CO2 emissions by world region since 1750

1

Fig. 1-2 The average annual temperature at the earth's surface has risen since the late 1800s, with
year-to-year variations (shown in black) being smoothed out (shown in red) to show the generalwarming trend. [2]

2

1.2.

Secondary Batteries and Lithium Air Batteries

Secondary battery (or rechargeable battery) is a type of electrical battery which can be chargedischarged. Secondary battery is one of energy storage device that can be used in all type ofelectrical equipment. As typical secondary batteries Lead–acid battery (Pb), Nickel-cadmium
battery (Ni-Cd), nickel metal hydride battery (Ni-MH) and Lithium-ion battery (Li-ion) are
widely available in our daily use. [3] Especially, Li-ion is most important one. From energy
density values of batteries (Table 1-1 & Fig. 1-3), [4] Li-ion battery and another type of lithium
batteries show a good energy density value in all commercial power batteries and have large
market share at the same time. With high energy density values, battery electric vehicles (BEVs)
and plug-in hybrid electric vehicles (PHEVs) are already under use found in civil transportation.
[5,6]

The materials used for cathode and anode material must show high practical specific density
and high cell potential. Based on the above principles, typical secondary batteries have chosen
Pd, Ni, and Li for anode metals or cathode metal materials. The cathode and anode material
also limit the electrolytes materials which are combination of various liquid or solid.

Table 1.1. A comparison among the rechargeable battery systems

3

Fig. 1-3 Energy density values of secondary batteries

The lead–acid battery (Pb) is a type of rechargeable battery first invented in 1859 by French
physicist Gaston Planté. It is the first type secondary battery ever created. The specific energy
density of lead–acid battery is around 30-40Wh/Kg (Table 1.1). [7] Following is the total
reaction.

2PbSO4(s) + 2H2O(l) ⇌ Pb(s) + PbO2(s) + 2H2SO4(aq) (E0cell= 2.05V) equation 1

In 1980s, nickel-cadmium battery (Ni-Cd) and nickel metal hydride battery (Ni-MH) has
become two widely used rechargeable batteries. The specific energy density of Ni-Cd and NiNH battery is around 40-60Wh/Kg (Ni-Cd) and 75-100Wh/Kg (Ni-Cd) (Table 1-1). The
abbreviation of the Ni-Cd battery is derived from nickel (Ni) and cadmium (Cd). The chemical
reaction at the positive electrode is similar in both of nickel-cadmium cell (Ni-Cd) and nickel
metal hydride battery (Ni-MH). The differences between Ni-Cd and Ni-MH are choice of theanode materials. [8]Ni-MH
H2O + M + e− = OH− + MH equation 1

4

Ni-CdCd + 2OH- = Cd(OH)2 + 2e− equation 2

Oxide electrode2NiO(OH)+2H2O + 2e−= 2Ni(OH)2+2OH- equation 3

After the Ni-Cd and Ni-MH batteries, a new type of battery that show a much higher
gravimetric energy density is necessary. Li-ion battery demonstrated high specific energy
density and low cost. As shown in Table 1-1 and Fig 1-3 lithium battery became the best choicefor power battery pack.
In 1970s, M. Stanley Whittingham has discovered the intercalation electrodes based on atitanium disulfide cathode and a lithium-aluminium anode. John Goodenough invented lithium
cobalt oxide as a cathode in 1980. In 1985, Li-ion battery's first commercial model wasdeveloped by Akira Yoshino, based on earlier research by John Goodenough utilizing graphite
as anode.
Lithium-ion battery (Li-ion) is a rechargeable battery that mainly relies on the movement oflithium ions between the positive and negative electrodes. Lithium-ion batteries use anintercalated compound as electrode material. Anode material is typically graphite. Currently
used cathode materials for lithium-ion batteries are lithium cobalt oxide (LiCoO2), lithium
manganate (LiMn2O4), lithium nickelate (LiNiO2), and lithium iron phosphate (LiFePO4),
which are widely commercially used. The typical energy density of full packing commercial
cell using various cathode materials is summarized in Table 1.2. [9-11]

5

Table 1.2. Energy density of Li-ion batteries anode material under full packing batteries.
Cathode materials

Nominal cell voltage

Energy density

LiCoO23.7v

140 mAh/g

LiMn2O4

3.7v

100 mAh/g

LiNiO23.3v

100 mAh/g

LiFePO4

3.6v

115 mAh/g

With the advancement of material technology, the metal-air battery is becoming a new hot thesecondary battery. The metal-battery was first discovered and researched in 1868 by Leclanche.
There are various metal-air batteries such as zinc-air battery, aluminium-air battery. In 1932,
zinc-air battery was designed and examined by Heise and Schumacher. Particularly Li-air
batteries could exhibit very high energy density values of 11680 Wh/Kg, which are comparable
to gasoline and ~10 times higher than that of Li-ion batteries (Fig. 1-4). [12]Fig. 1-4 Gravimetric energy density profile & Li-Air battery

This work deals with Li-air battery design and operation. Typically, lithium ions move acrossthe electrolyte between the anode and cathode. During discharge, the electrons follow theexternal circuit to do electrical work, and the lithium ions migrate to the cathode. Both non-6aqueous (Li2O2 or LiO2 as discharge product) and aqueous (LiOH as discharge product) Li-O2
batteries were considered. Aqueous batteries require a protective layer on lithium for negativeelectrode from reacting with water. In Li-air battery oxidation of lithium at the anode andreduction of oxygen at the cathode cause current flow. One of the typical structures of the Liair battery is shown in Figure 1-5. In detail, the electrolytes are different between four types of Liair batteries, there are aprotic, aqueous, solid-state, and hybrid aqueous/ aprotic (Fig 1-6). [13,14]

Fig. 1-5 Schematic representation of typical Lithium Air (Li-air) battery

Fig. 1-6: Schematic representation of different types of Li-air batteries (Figure adopted
from Chem. Rev., 2014, 114, 5611–5640)
7

Lithium metal is the typical choice of anode. Lithium has a high specific capacity (3840 mAh/g)
compared to other metal-air battery materials (820 mAh/g for zinc and 2965 mAh/g foraluminium). At the anode, lithium metal releases electrons via oxidation under electrochemical
potential forces. [14,16] The half-reaction is:
Li = Li+ + e− equation 1

Li-air battery with high performance and energy density works under non-aqueous electrolyte.
The reactions in Li-air battery are:
2Li + 1/2O2 ⇌ Li2O equation 2
2Li + O2 ⇌ Li2O2 equation 3
Total: 2Li+ + 2e− + O2 = Li2O2 (E0= 2.96 V vs Li/Li+) equation 4

Li-air battery with high performance and energy density works under aqueous electrolyte. The
reactions in Li-air battery are:Alkaline: O2 + 2H2O + 4e− = 4OH− (E0= 3.43 V vs Li/Li+) equation 5
Acid: O2 + 4e− + 4H+ = 2H2O (E0= 4.26 V vs Li/Li+) equation 6

Cathode is mixed with electrocatalyst. OER catalysts help in breaking of LixO2. The halfreaction is:
Li+ + O2 + e- = LixO2 equation 7

Li-air batteries do not have issues with fuel infrastructure. Then their specific energy density
is much higher than the secondary batteries such as Ni-MH and Li-ion. The relationshipbetween electrolyte and oxygen in cathode is shown in Figure 1-7. With equations 4-6, Li-air
battery which operates under non-aqueous electrolyte could provide higher energy density
than in aqueous electrolyte. Challenges to this battery systems are improvement in specificenergy density and overall energy efficiency, charge-discharge cyclability, dendrite formationon all electrodes, instability of electrolytes and catalysts in the oxygen atmosphere,
conductivity of electrolytes and electrodes, and so on. Charge-discharge current density of8typical Li-air batteries are 0.1−0.5 mA/cm2. The major bottleneck of efficiency is oxygen
reduction reaction and oxygen evolution reaction kinetics and uncontrollable side reactions of
Li-OX systems.

Fig. 1-7 Models of the reaction zones for catalytic reduction of oxygen: (a) a “three- phase reactionzone” for aqueous electrolyte metal/air battery and (b) a “two-phase reaction zone” for non-aqueous
electrolyte Li–air battery (the original figure is insignificantly modified) [17]In Li-air battery, cathode works on oxygen reduction reaction (ORR) and oxygen evolution
reaction (OER). ORR and OER in nonaqueous systems follow the following mechanisms:
ORR:
O2 + 2e− = O2−
O2− + Li+ → LiO2
2LiO2 → Li2O2 + O2

OER:
Li2O2 = 2Li+ + O2 + 2e−

Under discharge, Li+ containing non-aqueous electrolyte absorb the O2 from air or oxygen gas
and turns O2 to O2− and binds with Li+ to form Li2O (Fig.1-7 b), on the surface of the electrode.
ORR and OER catalysts play an important role in determining efficiency and cyclability of Li-

9air battery. [18,19]
The choice of electrolyte is important in nonaqueous electrolyte-based Li-air batteries. In suchelectrolytes superoxide radical (O2-) formed by ORR shall be stable during discharge cycle.
Some type of Li-ion batteries electrolytes could be used for Li-air batteries as well. But the Liair batteries works in oxygen rich environments, and electrolytes shall be tested carefully. [20]Following are requirements for electrolytes in Li-air batteries
1. stability toward reaction with lithium metal
2. high boiling point and low volatility
3. high oxygen solubility and diffusivity
4. low viscosity to improve the rate performance

The lithium salts with LiPF6, lithium bis[(trifluoromethyl)sulfonyl]imide (LiTFSI), LiClO4,
LiCF3SO3, LiBF4, LiCl, and lithium bis(oxalato)borate (LiBOB) are supporting electrolyte
usually. Specifically, for lithium air battery following are requirement for salts
1. Solubility is high enough in the solvent which could support smooth ion transport
2. Inert to the solvent and other cell components
3. Inert to the aggressive oxygen reduction species

Lithium bis[(trifluoromethyl) sulfonyl] imide (LiTFSI) is chosen for supporting electrolyte.
LiI is employed as mediator.

10

1.3.

Electrocatalyst for Cathode

It is important to have ORR and OER activities of electrocatalysts for the uses for Li-air battery.
Carbon based materials can keep large specific surface area and conductivity, which makes it
standard materials. The Oxygen Reduction Reaction (ORR) and the Oxygen Evolution
Reaction (OER) are two type metal catalysed reaction. Under Li-air battery, ORR and OER
activity is key for battery performance.

1.3.1. Oxygen Reduction Reaction (ORR)
1.3.1.1. Mechanism of ORR

The ORR is a complex process with diverse intermediates, the nature of which is influenced
by the catalyst type and even by the reaction medium. Table 1.3 provides an overview about
the ORR mechanism in various media, highlighting distinct intermediates and their associatedthermodynamic potentials. This multifaceted understanding underscores the intricate
dynamics of ORR, emphasizing the pivotal role of catalyst and environment in shaping thereaction pathway and thermodynamic considerations.

Table 1.3: Thermodynamic electrode potentials of electrochemical oxygen reduction reaction.

=
=
=
=
=
=
=
=

11

Oxygen reduction reaction (ORR) could be classified as 4e- process or 2e- process. 4e- process
is key to produce water. Hydrogen peroxide is formed via in 2e- process. In fuel cell, 4epathway is preferred. In industrial H2O2 production, 2e- reduction pathway is preferred. [21]When the catalysts for Air-battery or fuel cell are designed larger electrochemical surface area
has to be ensured. Usually, carbon-based supports are chosen.

1.3.1.2. Mechanism of ORR on Carbon Materials
ORR on graphite and glassy carbon: The following mechanism has been proposed for ORR
catalysts. The following mechanism has been proposed.
𝑂2 → 𝑂2(𝑎𝑑𝑠)equation 1

𝑂2 + 𝑒− = [𝑂2(𝑎𝑑𝑠)]-

equation 2

𝑂2 (𝑎𝑑𝑠) → 𝑂2 [𝑎𝑑𝑠] -equation 3𝑂2−(𝑎𝑑𝑠) + 𝐻2𝑂 → 𝐻𝑂2 + 𝑂𝐻−

equation 4

𝐻𝑂2 + 𝑒− = 𝐻𝑂2−(𝑎𝑑𝑠)equation 5

𝐻𝑂2−(𝑎𝑑𝑠) → 𝐻𝑂2−

equation 6

Corresponded species adsorbed on the electrode surface are marked as subscript ads. The
reactants and products in Reaction 3 are two different forms of superoxide ions. [22]12

1.3.1.3. ORR on Carbon Nanotubes
Carbon nanotubes (CNTs) have attracted significant interest due to their unique electronic,
mechanical, and thermal properties. These properties make CNTs promising materials forvarious applications, such as energy storage, biosensors, and catalysis. In particular, thecatalytic properties of CNTs have been extensively investigated, and they have been found tobe effective in catalyzing many chemical reactions, including the oxygen reduction reaction(ORR). [23]The activity of CNTs in ORR is strongly influenced by their preparation method. In the dihexylhydrogen phosphate synthesis method, the CNTs showed a catalytic activity for ORR througha two-electron process. This method involved the formation of a thin film of the dihexylhydrogen phosphate on a glassy carbon electrode, followed by the deposition of CNTs. The
CNTs showed a high electrocatalytic activity for ORR due to the presence of nitrogencontaining functional groups on their surface.
On the other hand, when poly-diallyl dimethylammonium chloride was used to synthesize
multi-walled carbon nanotubes, the electron transfer number was found to be between 3 and3.5. The higher electron transfer number suggests that the CNTs prepared by this method had
a higher number of active sites for ORR. The high activity of CNTs in ORR makes thempotential candidates for use in fuel cells and other electrochemical devices.
To further enhance the performance of CNT-based catalysts for ORR, efforts are being madeto modify the surface of the CNTs to increase their hydrophilicity, promote gas scavenging,and improve their durability. These modifications include doping the CNTs with heteroatoms,
such as nitrogen or boron, and introducing defects in the CNT structure. Overall, the uniqueproperties and versatile applications of CNTs make them an exciting area of research for thedevelopment of new and improved electrocatalytic materials.

131.3.1.4. ORR on Heteroatom Doped Carbon Atoms
Doping carbon with heteroatoms has been shown to be an effective way of enhancing ORR
activity. Nitrogen has been the most commonly used dopant. In fact, doping carbon fibres withnitrogen has been shown to shift the ORR potential by nearly 70 mV, and the number ofelectron transfers was close to 4. Other heteroatoms such as boron, sulfur, fluorine, andphosphorus can also be used to dope carbon and enhance ORR activity, although the exact
mechanism behind this is not yet fully understood. It is believed that the introduction ofheteroatoms into the carbon structure creates active sites near the heteroatom and facilitates thebreaking of the O=O bond in O2, leading to enhanced ORR activity. [24]1.3.1.5. ORR on Pretreated Carbon Surface
Electrode surface pretreatment has been found to be an effective way to improve ORR
performance. Various methods such as vacuum heat treatment, electrode polishing, radio
frequency plasma treatment, in-situ laser treatment, low-pressure heating, and electrochemical
oxidation have been used to pretreat the electrodes. These methods have been found to increase
the surface area of the electrodes to generate more functional groups and defects and expose
new edges. This leads to more active sites on the electrode surface, which can enhance the ORR
performance. However, the optimal pretreatment method may vary depending on the specific
type of electrode material and the intended application. [25]1.3.1.6. ORR Activity on Precious Metals
Platinum (Pt) is considered to be the most efficient catalyst for ORR. Despite efforts to find asingle metal with similar activity, none have been found to match platinum. While the exact
mechanism by which platinum catalyses ORR is not yet fully understood, research hassuggested a possible pathway involving multiple intermediates as illustrated in Figure 1.8.
According to this pathway, oxygen is fully reduced to water by losing 4 electrons without any
intermediate states being formed during the process. [26]14Fig 1.8: Mechanism of ORR on Pt

As we can see in Figure 1.6, O2 can be reduced directly to H2O with a rate constant of K1, or
it can be reduced to H2O2 via an intermediate formation with a rate constant of K2. In addition,
this intermediate can be reduced to HO- with a rate constant K3 or can be desorbed in theelectrolyte with a rate constant K5 or can be decomposed at the electrolyte surface with a rate
constant K4. It is widely accepted, however, that the most favourable route is to form water
directly with the electron number of 4 transfer.
Two mechanisms were proposed based on DFT calculations. They are the association
mechanism and the dissociation mechanism. The association mechanism is suitable for regionsof high current density.
The dissociation mechanism is suitable under low current density regions where the O=O bondin O2 splits and atomic O forms OH- and H2O. Other metals (such as Au, Cu, Pd, Ir, and Rh)
can also exhibit ORR activities, but no other metal can maintain or exceed the catalytic activityof Pt.

15

1.3.1.7. Fuel-cell and Li-air Battery
ORR is well demonstrated and highly efficient in nature. The specific capacity (mass energy
density) with Lithium is 3840 mAh/g or 43MJ/kg and the specific energy of hydrogen is 141.6
MJ/kg. As a comparison, gasoline is 46.4 MJ/kg, diesel is 44.8 MJ/kg and Li-ion battery is
0.46-0.73MJ/kg. The metals for ORR activity are shown in Figure 1-9 (volcano plot of ORR
catalyst).
Regarding ORR activity, Pt is top of all materials, also the ORR catalyst is mainly used for fuelcell system.

volcano plot of ORR catalyst

Fig. 1-9 Trends in oxygen reduction activity plotted as a function of the oxygen binding energy[26]Fuel cells have many advantages over traditional power generation methods, such as internal
combustion engines, because they can operate at higher efficiency, lower noise levels, andproduce fewer emissions. They are also scalable, which means they can be used as power foranything from small portable devices to large industrial applications. Fuel cells are particularly
attractive for transportation applications because they have the potential to provide a zeroemission source of power, which is critical for reducing greenhouse gas emissions andcombating climate change. [27]16There are several types of fuel cells, each with different operating characteristics and materials.
For example, proton exchange membrane (PEM) fuel cells are widely used in transportation
applications because they can operate at low temperatures and have a high power density. Solidoxide fuel cells (SOFCs) operate at high temperatures and are typically used in large stationary
power generation applications.
Despite their many advantages, fuel cells still face several challenges that limit theirwidespread adoption. One major challenge is the cost of materials and manufacturing, whichis still relatively high compared to other power generation methods. Another challenge is thelimited availability of hydrogen fuelling infrastructure, which is necessary for hydrogen fuelcells to be used in transportation applications. Researchers and engineers are working toaddress these challenges and improve the efficiency and cost-effectiveness of fuel cells, inorder to make them more accessible and practical for a wide range of applications.
Typical Proton Exchange Membrane Fuel Cell (PEMFC) design is shown below in Figure 110. The reaction of fuel cell is:𝐻2 = 2𝐻 + + 2𝑒 −𝐸 0 = 0 𝑉 𝑣𝑠 𝑆𝐻𝐸

1
𝑂 + 2𝐻 + + 2𝑒 − = 𝐻2 𝑂
2 2

17

𝐸 0 = 1.23 𝑉 𝑣𝑠 𝑆𝐻𝐸

Fig 1-10. Schematic Representation of Proton Exchange Membrane Fuel Cell (PEMFC)

When the PEMFC works, the ORR happens in cathode where the catalyst layer is loaded. The
electrochemical performance of fuel cell is decided on the surface which is marked under red
line in Figure 1-11. [28]Fig 1-11. Oxygen Reduction Reaction (ORR) & Proton Exchange Membrane Fuel Cell (PEMFC)

18

1.3.2. Oxygen Evolution Reaction (OER)
1.3.2.1.

Mechanism of OER

The Oxygen Evolution Reaction (OER) is also called Water oxidation reaction, which is oneof the half reactions of water splitting. Basic reaction is
2H2O = O2 + 4H+ + 4e−

Oxidation (generation of dioxygen)(a)4H+ + 4e− = 2H2

Reduction (generation of dihydrogen)(b)

2H2O = 2H2 + O2

Total Reaction(c)Equation (b) (HER) and Equation (c) (OER) are two concurrent catalytic half-cell reactions.
Though oxygen evolution is a 4-electron process, it is more complicated than evolution ofhydrogen, as several surface-adsorbed intermediates are involved. The electrocatalysis processof water in each process must be discussed with respect to voltage and efficiency losses. The
HER using selected noble metals setting exhibits very high exchange current density j0, which
is a measure of the internal turnover frequency of an electrochemical half-cell process (Figure1-12). [29,30]
In electrocatalysis, overpotential is a fundamental concept of characterizing catalytic processes
on surfaces, which is important in OER and ORR activity. The overpotential is generally
considered to be a dynamical phenomenon, which can be divided into various factors such as
ohmic overpotential or transport overpotential in the process of charge flow.

19Figure 1-12. Catalytic reactions associated with electrochemical water electrolysis. An external
voltage, symbolized by the battery symbol, drives the evolution of hydrogen at the cathode (HER) andthe evolution of oxygen at the anode (OER). Protons are migrating from anode to cathode. Bothmechanisms are depicted assuming a sequence of proton-coupled single-electron redox reactions.
While HER shows one adsorbed intermediate, OER has three. The spheres symbolize a metalelectrode, for example, Pt, covered with an oxide layer. The numbers in parentheses refer to chemical
equations given in the text. [31]20

1.3.2.2. Mechanism of OER on Carbon Materials
Carbon materials are widely used in electrocatalysis. From the discussion in 1.3.2.1, OER
happened on the surface of the noble metals. How to keep the large area is a challenge withcatalyst. In general, as results of OER and HER bubbles could be found on the surface of theelectrode surface, so the speed of gas scavenging could limit the activity.
Improved hydrophilicity, keeping a large surface may resolve the limited gas diffusion on the
catalyst surface. [31]1.3.2.3. OER Activity on Metals
Metal selection for OER can be based on the volcano plot of ORR catalyst, as shown in Figure
1-13. Among the metals studied for ORR, Ru exhibits the best performance, followed closely
by Pt. However, when discussing OER activity, it is important to consider heterogeneous OER,
which is highly dependent on the surface where the reaction occurs and is influenced by the
pH of the solution. In fuel cells and Li-air batteries, the pH during operation is usually below
7. According to Figure 1-14, even under ideal conditions, OER activity with Ru and Pt catalysts
operating at 6 mV/s and 1600 rpm in 0.1 M HClO4 at room temperature only reaches 30% of
the theoretical values. [32]Fig. 1-13 Trends in oxygen evolution activity plotted as a function of the oxygen dis-binding energy
21Fig 1-14. First quasi stationary OER scan for bulk and nanoparticle catalysts of Ru, Ir, and Pt
recorded with 6 mV/s and 1600 rotations per minute (rpm) in deaerated 0.1 M HClO4 at RT. The
current is normalized to the number of surface sites determined from CO stripping experiments.
[33]

22

1.3.2.4. Li-Air Battery Using Metals
In Li-air batteries, the metal catalysts used for OER are crucial for the battery's performance.
The most commonly used metals are noble metals, such as platinum (Pt), ruthenium (Ru), andiridium (Ir), due to their high catalytic activity for OER. However, their scarcity and high costlimit their practical application. Therefore, researchers have been investigating alternative
metal catalysts that are more abundant and cost-effective, such as transition metals and theiroxides, including cobalt (Co), manganese (Mn), nickel (Ni), iron (Fe). These metals and theiroxides have shown promising OER activity, but their catalytic activity is generally lower thanthat of noble metals. Therefore, improving the catalytic activity of these metals and their oxides
is a key research area for developing more efficient and cost-effective Li-air batteries.
Catalyst design aims to achieve high performance at a lower cost, and for this reason, Ir is often
the best choice, even though it may lose some activity under acidic conditions during OER
activity. Both fuel cells and Li-air batteries use the same site for ORR and OER reactions.
However, when ORR catalysts are used under OER conditions, their performance is significantly reduced, and they may even become damaged. This is because, under acidic conditions,water binds to the catalyst surface and irreversibly removes one electron and one proton, forming metal hydroxide. In alkaline solutions, typically, an oxide surface is presumed to form prior
to oxygen evolution during OER.

23

1.3.3.

Application of Bi-functional Catalyst and Li-Air Battery Design

Developing improved catalysts for ORR and OER is the key to the advancement of in metalair batteries.
In this work, a catalyst needs to be designed for the Li-air battery in which new catalyst would
work for ORR and OER. That means this catalyst must deal with two key problems at sametime.
In this study, a catalyst is needed to be designed for Li-air batteries that can operate efficiently
under both ORR and OER conditions. This means that the catalyst must address two criticalchallenges: firstly, it must maintain high ORR and OER activity, and secondly, it should exhibit
stable performance under both ORR and OER conditions. It is the catalyst with Pt which works
for ORR activity and Ir for OER activity. In section 1.2 the Li-air battery has been discussed;
the catalyst is loaded on carbon-coated Ni mesh. The battery structure is shown in Figure 1-15.

Fig 1-15. Structure of Li-air battery

24

1.4.

Introduction on Carbon-metal Based ORR and OER Catalyst

Carbon materials loaded with nanomaterials have been used in heterogeneous catalysis. These
kinds of carbon-based materials have been used in catalysis as catalysts or even as supports ofcatalysts. Advantages are i) high chemical stability, ii) high thermal stability, iii) less corrosion
capability, iv) easy recovery after reaction or synthesis and v) easy modification by chemicalor physical method. However, over the surface of the carbon, their acid–base character andredox properties could be controlled by concentration and nature of the organic functionalgroups that are bearing different heteroatoms such as O, N, H, Cl, S, etc. (Fig 1-16). These
affect morphological properties of carbon and show crucial role in catalytic behaviour. [34]Fig 1-16. Organic functional groups on carbon materials

25

1.5.

Facet Controlled Catalysis

The facet-controlled ORR has gained significant global research attention for achieving highperformance. Low-index Pt nano-surfaces have been extensively studied in perchloric acid. In
perchloric acid, Pt (100) << Pt (111) ̴ Pt (110) in terms of activity has been reported. However,when operating within an acidic aqueous electrolyte system, Pt (100) is more reactive than Pt(111) due to the surface coverage of Pt (111) by bisulfate ions. It was further established thatthe arrangement of surface atoms, i.e., the morphological features, affects the catalytic
performance. Shape-controlled synthetic strategies for transferring active catalytic surfaces
from single crystals to practical nanophases show enhancement of the ORR activity of platinum.
El-Sayed et al. successfully synthesized different facets of Pt, including nano-tetrahedra with
(111) and nano-cubic composition of (100) as well as "approximately spherical" nanocrystals
containing a mixture of {111} and {100} surfaces. [35]Sun et al. conducted research on the synthesis of one-sided Pt nano-cubes (100) using a hightemperature method and found that the resulting catalyst exhibited a 2-fold higher ORR(oxygen reduction reaction) activity compared to commercially available Pt catalysts. The
group also demonstrated that 7 nm (100) Pt nano-cubes showed better activity than othermorphological forms of nanoparticles, highlighting the importance of facets as well as theshape dependence of nano-catalysts.
Another research group led by Xia et al. reported the synthesis of Pt concave nano-cubes withhigh-refractive-index faces such as {510}, {720}, and {830}. These catalysts exhibited higher
electrocatalytic activity per unit surface area compared to catalysts with low-index planes, suchas {100} and {111}. Despite the observed higher activity of these higher-index facets, theunderlying mechanism remains unclear. Additionally, these highly faceted nanocrystals
exhibited lower mass activity compared to other highly active ORR catalysts.
In summary, facet-controlled synthesis of Pt nano-catalysts has been shown to be a promisingstrategy for enhancing ORR activity. The surface morphology and atomic arrangement of Pt
nanocrystals play critical roles in determining their electrocatalytic performance. High-index
facets have been shown to exhibit higher activity, although the mechanism behind this is not
yet fully understood. Further research is needed to optimize nano-catalyst synthesis and design,with a particular focus on balancing activity and stability for practical fuel cell applications.

26

1.6.

Enhancement of Catalytic Activity of These Alloys

Bimetallic core-shell nanoparticles have been shown to exhibit improved activity and stability
compared to their bulk counterparts, due to the unique synergistic effects between the twodifferent metals. The core-shell structure consists of a metallic core surrounded by a shell layerof another metal. The metal shell can act as a protective barrier against dissolution, preventing
the leaching of non-Pt metals, while the metal core maintains the activity of the catalyst.
Furthermore, the properties of the core-shell structure can be further tuned by controlling thesize, composition, and morphology of the particles. For example, by varying the thickness ofthe shell layer, the activity and selectivity of the catalyst can be adjusted. In addition, the useof highly dispersed alloy nanoparticles can also improve the performance of the catalyst, as thehigh surface area to provide more active sites for the reaction.
In recent years, various methods have been developed for the synthesis of core-shell
nanoparticles, including chemical reduction, solvothermal synthesis, and galvanic replacement.
These methods allow precise control over the size, composition, and morphology of theparticles, enabling the development of highly efficient and stable electrocatalysts for ORR
applications.
Overall, the use of bimetallic core-shell nanoparticles offers a promising approach forovercoming the limitations of traditional alloy catalysts and provides a path for the design anddevelopment of highly efficient and stable ORR catalysts. [36]

27

1.7.

Synthesis of Core Shell Nanoparticles:

There are various strategies for the synthesis of core-shell nanoparticles.
A core metal is selected and a shell was deposited on this already formed core.
Removal of unwanted constituents from alloys also can be carried out.
The alloy is treated in such a way that one of the alloy constituents’ segregates to the surface
to form a shell.
Figure 1.17 schematically illustrates the diverse methodologies employed in the developmentof core-shell nanoparticles. Researchers are benefited from the versatility in synthesis methods,
allowing them to tailor nanoparticles to specific requirements.

Fig 1.17: Various synthetic methods for core shell nanoparticles(Figure adapted from J. Phys. Chem. Lett., 2013, 4, 3273–3291)

In this work, a carbon-supported Pt/Ir alloy nano-particles was synthesized and examined for
Li-air battery.

28

1.8.

Design and Utilization of FAB Based Catalyst

Carbon has been used as the support for metal loading for many years in industrial catalyst. In
electrocatalyst filed, oil-furnace blacks and acetylene blacks are two main types of carbon black
being used as supports for Pt/C catalyst. In some research, carbon can affect the dispersion of
the Pt particles. Usually, acetylene blacks typically have surface areas below 100 m2g-1, andfurnace blacks show surface areas ranging from 20 to 1500 m2g-1, which were summarized inTable 1.4.

Table 1.4 Carbon blacks that have been used as support for Pt catalysts in PEMFCs
CarbonSupplier

Type of carbon

BET surface area

DBP adsorption(m2 g−1)a(units)b

Vulcan XC72

Cabot Corp.

Furnace black

250

190

Black Pearls 2000

Cabot Corp.

Furnace black

1500

330

Ketjen EC300J

Ketjen Black International

Furnace black

800

360

Ketjen EC600JD

Ketjen Black International

Furnace black

1270

495

Shawinigan

Chevron

Acetylene black80-

Denka black

Denka

Acetylene black

65

165

a BET: Brunauer–Emmett–Teller method.
b DBP: dibutyl phthalate number (measure of carbon void volume).

Acetylene black (AB) (Fig 1-18) is one of carbon black, which has lower polycyclic aromatichydrocarbon (PAH) content, and function group is less than 1%. When carbon support shows
better affinity to metal nanoparticle, such affinity is key to control the nanoparticles size toenable larger surface area. When appropriate functional groups are present on the surface ofAB particles, an increase in their surface area is observed.
Pt/Ir alloy nanoparticles and FAB as carbon support, was combined to form a new class ofelectrocatalyst, which is Bifunctional Pt/Ir Nano-particles Decorated Functionalized Acetylene
Black. These systems are expected to exhibit higher performance in ORR and OER at sametime along with long life.

29

Fig 1-18. Structure (a) and TEM (b) of Acetylene black

30

1.9.

Important Evaluation Methods and Basic Principles

Electrochemical Measurements
Three-electrodes set up was used for cyclic voltammetry. Typical three-electrodes set up isrepresented in Figure 1-23. Under three-electrodes system, current flows between the working
electrode and the counter electrode was measured. Electric potential on working electrode has
been controlled by an independent reference electrode, that means the electric potential on
working electrode could be kept and monitored steadily.

Fig. 1-23 three-electrodes assay

In this study, aqueous and organic electrolytes were chosen for ORR performance
determination. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were carriedout under aqueous electrolytes. Cyclic voltammetry (CV) was measured under organic
electrolytes as well.
Cyclic voltammetry (CV) is an electrochemical technique that is supported by the Nernst
equation. The potential of the working electrode undergoes a smooth change that is measured
against reference electrode, as shown in Figure 1-24. The Figure 1-24 is forward scan, whichstarts from a greater potential (a) and ends at a lower potential (d). The potential maximum (d)are called as the switching potential, where the voltage is sufficient enough to complete anoxidation or reduction. From (d) to (g) is positive scans, which turns to the reverse scan
thereafter. The scans speed is the slope between (a) to (d). Figure 1-24 shows a cyclic
voltammetry image resulting from an reduction and oxidation, which demonstrate reversible
reaction. The reduction occurs during (a) and (d).
Linear sweep voltammetry (LSV) is another voltametric method. Under sweeping the potential
between the working electrode and a reference electrode linearly by time, voltammogram is31obtained as shown in Figure 1-25.

Fig. 1-24 CV Excitation Signal

Fig. 1-25 Voltammogram of a Single electron oxidation-reduction

32

Fig. 1-26 Linear potential sweep33

1.10. Conclusion and Outlook about This Research
Li-air battery system is one of metal batteries; this type of battery could keep very high energy
density, however, the limited of electrocatalyst is bottleneck of this technology. Bifunctional
Pt/Ir Nano-particles Decorated Functionalized Acetylene Black as new type of catalyst, which
has dual catalytic activity both for ORR and OER at once, will demonstrate advantage of thiselectrocatalyst design.

34

References[1] Our World in Data. Retrieved, < https://ourworldindata.org>, (2019).
[2] NASA GISS Surface Temperature Analysis (v4), <https://data.giss.nasa.gov/gistemp/graphs_v4/>,(2019).
[3] Reddy, Thomas B. "David Linden Editor." (2002).
[4] Aravindan, V., Gnanaraj, J., Lee, Y. S., & Madhavi, S. (2013). LiMnPO 4–A next generation
cathode material for lithium-ion batteries. Journal of Materials Chemistry A, 1(11), 3518-3539.
[5] 独立行政法人 新エネルギー・産業技術総合開発機構(NEDO), 「ＮＥＤＯ二次電池技術開発ロード
マップ (Battery RM2010)」 (2010).
[6] 独立行政法人 新エネルギー・産業技術総合開発機構(NEDO), 「NEDO 二次電池技術開発ロードマップ 2013 （Battery RM2013）」 (2013).
[7] May, G. J., Davidson, A., & Monahov, B. (2018). Lead batteries for utility energy storage: A review.
Journal of energy storage, 15, 145-157.
[8] Putois, F. (1995). Market for nickel-cadmium batteries. Journal of Power Sources, 57(1-2), 67-70[9] Kwon, S. J., Lee, S. E., Lim, J. H., Choi, J., & Kim, J. (2018). Performance and life degradation
characteristics analysis of NCM LIB for BESS. Electronics, 7(12), 406.
[10] Vicente, J. R., Kordesch, M. E., & Chen, J. (2021). Stabilization of mixed-halide lead perovskites
under light by photothermal effects. Journal of Energy Chemistry, 63, 8-11
[11] "The Nobel Prize in Chemistry 2019". Nobel Prize. Nobel Foundation. 2019. Retrieved 1
January 2020[12] 国立研究開発法人 物質・材料研究機構(NIMS), 「リチウム空気電池について」, (2018).
[13] Girishkumar, G., McCloskey, B., Luntz, A. C., Swanson, S., & Wilcke, W. (2010). Lithium− airbattery: promise and challenges. The Journal of Physical Chemistry Letters, 1(14), 2193-2203.
[14] Abraham, K. M., & Jiang, Z. (1996). A polymer electrolyte‐based rechargeable lithium/oxygen
battery. Journal of the Electrochemical Society, 143(1), 1.
[15] Girishkumar, G., McCloskey, B., Luntz, A. C., Swanson, S., & Wilcke, W. (2010). Lithium− airbattery: promise and challenges. The Journal of Physical Chemistry Letters, 1(14), 2193-2203.
[16] Ogasawara, T., Débart, A., Holzapfel, M., Novák, P., & Bruce, P. G. (2006). Rechargeable Li 2O2electrode for lithium batteries. Journal of the American Chemical Society, 128(4), 1390-1393.
[17] Kraytsberg, A., & Ein-Eli, Y. (2011). Review on Li–air batteries—Opportunities, limitations andperspective. Journal of Power sources, 196(3), 886-893.
[18] Peng, Z., Freunberger, S. A., Hardwick, L. J., Chen, Y., Giordani, V., Bardé, F., ... & Bruce, P. G.
(2011). Oxygen reactions in a non‐aqueous Li+ electrolyte. Angewandte Chemie International
Edition, 50(28), 6351-6355[19] Geng, D., Ding, N., Hor, T. A., Chien, S. W., Liu, Z., Wuu, D., ... & Zong, Y. (2016). From lithium‐oxygen to lithium ‐ air batteries: challenges and opportunities. Advanced Energy Materials, 6(9),1502164.
[20] Di Censo, D., Exnar, I., & Graetzel, M. (2005). Non-corrosive electrolyte compositions containing
perfluoroalkylsulfonyl imides for high power Li-ion batteries. Electrochemistry communications, 7(10),1000-1006.

35

[21] Taylor, R. J., & Humffray, A. A. (1975). Electrochemical studies on glassy carbon electrodes: II.
Oxygen reduction in solutions of high pH (pH> 10). Journal of Electroanalytical Chemistry and Interfacial
Electrochemistry, 64(1), 63-84.
[22] Singh, S. K., Takeyasu, K., & Nakamura, J. (2019). Active sites and mechanism of oxygen reduction
reaction electrocatalysis on nitrogen‐doped carbon materials. Advanced Materials, 31(13), 1804297.
[23] Tang, H., Chen, J. H., Huang, Z. P., Wang, D. Z., Ren, Z. F., Nie, L. H., ... & Yao, S. Z. (2004).
High dispersion and electrocatalytic properties of platinum on well-aligned carbon nanotube
arrays. Carbon, 42(1), 191-197.
[24] Maldonado, S., & Stevenson, K. J. (2005). Influence of nitrogen doping on oxygen reduction
electrocatalysis at carbon nanofiber electrodes. The Journal of Physical Chemistry B, 109(10), 47074716.
[25] Šljukić, B., Banks, C. E., & Compton, R. G. (2005). An overview of the electrochemical reductionof oxygen at carbon-based modified electrodes. Journal of the Iranian Chemical Society, 2, 1-25.
[26] Zhang, S., Yuan, X. Z., Hin, J. N. C., Wang, H., Friedrich, K. A., & Schulze, M. (2009). A review ofplatinum-based catalyst layer degradation in proton exchange membrane fuel cells. Journal of Power
Sources, 194(2), 588-600.
[27] Tiwari, J. N., Lee, W. G., Sultan, S., Yousuf, M., Harzandi, A. M., Vij, V., & Kim, K. S. (2017). Highaffinity-assisted nanoscale alloys as remarkable bifunctional catalyst for alcohol oxidation and oxygen
reduction reactions. ACS nano, 11(8), 7729-7735.
[28] Yin, X., Lin, L., Chung, H. T., Babu, S. K., Martinez, U., Purdy, G. M., & Zelenay, P. (2017). Effects
of MEA fabrication and ionomer composition on fuel cell performance of PGM-free ORR catalyst. ECSTransactions, 77(11), 1273.
[29] Ghosh, S. K., & Rahaman, H. (2019). Noble metal–manganese oxide hybrid nanocatalysts.
In Noble Metal-Metal Oxide Hybrid Nanoparticles (pp. 313-340). Woodhead Publishing.
[30] Dotan, H., Landman, A., Sheehan, S. W., Malviya, K. D., Shter, G. E., Grave, D. A., ... & Grader,
G. S. (2019). Decoupled hydrogen and oxygen evolution by a two-step electrochemical–chemical cyclefor efficient overall water splitting. Nature Energy, 4(9), 786-795.
[31] Ghosh, S. K., & Rahaman, H. (2019). Noble metal–manganese oxide hybrid nanocatalysts.
In Noble Metal-Metal Oxide Hybrid Nanoparticles (pp. 313-340). Woodhead Publishing.

[32] Nørskov, J. K., Rossmeisl, J., Logadottir, A., Lindqvist, L. R. K. J., Kitchin, J. R., Bligaard, T., &Jonsson, H. (2004). Origin of the overpotential for oxygen reduction at a fuel-cell cathode. The Journalof Physical Chemistry B, 108(46), 17886-17892.
[33] Tahir, M., Pan, L., Idrees, F., Zhang, X., Wang, L., Zou, J. J., & Wang, Z. L. (2017). Electrocatalytic
oxygen evolution reaction for energy conversion and storage: a comprehensive review. Nano
Energy, 37, 136-157.
[34] Kasprzak, A., Zuchowska, A., & Poplawska, M. (2018). Functionalization of graphene: does theorganic chemistry matter. Beilstein journal of organic chemistry, 14(1). 2018-2026.
[35] Wang, Y., Nie, Y., Ding, W., Chen, S. G., Xiong, K., Qi, X. Q., ... & Wei, Z. D. (2015). Unification of
catalytic oxygen reduction and hydrogen evolution reactions: highly dispersive Co nanoparticles
encapsulated inside Co and nitrogen co-doped carbon. Chemical communications, 51(43), 8942-8945.
[36] Hong, J. W., Kang, S. W., Choi, B. S., Kim, D., Lee, S. B., & Han, S. W. (2012). Controlled synthesisof Pd–Pt alloy hollow nanostructures with enhanced catalytic activities for oxygen reduction. ACS nano,6(3), 2410-2419.

36

2. Chapter 2Material Preparing Discussion.

2.1.

Abstract

In this work, we report a high feasibility catalyst design on Acetylene Black (AB) based
nanoparticles loading materials. The AB needs to be pre-processed before loading with metal
nanoparticles. Pt alloy nanoparticles have been chosen to enhance the activity of the AB, withrespect to oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The
successful formation of bifunctional Pt/Ir nanoparticles decorated functionalized Acetylene
Black, such as FAB180-Pt and FAB(x)-Pt/Ir catalyst, has been demonstrated. Materials
characterization was carried out by impedance analysis, scanning electron microscopy-energydispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM),
thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS).

37

2.2.

Introduction

The challenge of controlling and reducing global warming is a worldwide concern, and finding
alternative energy sources is crucial to addressing this issue. [1] Use for renewable energy is
one of the best solutions, and wind and solar power are becoming more prevalent methods ofgenerating electricity. The development of batteries that can efficiently store and discharge
electricity will further enhance the viability of renewable energy sources. The use of clean
energy systems is becoming increasingly desirable, not only to reduce greenhouse gas
emissions but also to reduce reliance on fossil fuels, which are finite resources. The adoptionof renewable energy and the implementation of clean energy systems are essential steps inachieving sustainable development and combating climate change. It is crucial that individuals,
businesses, and governments work together to invest in and promote the use of renewableenergy sources and clean energy systems.
According to Figure 2-1, metal-air batteries have highest energy densities compared to othertypes of batteries. This is because they use anodes made from pure metal and an external
cathode of ambient air. Due to the small amount of actual mass in the battery, the calculated
energy density is high.[2] Aluminium, which has 3 valence electrons compared to lithium's 1
valence electron, also contributes to the high energy density. The Ragone plot shown in Figure
2-1 confirms that metal-air batteries have good energy density. Chemical energy storage isbecoming increasingly important as a way to store electricity, and metal-air batteries are apromising technology in this regard. By further developing and optimizing these batteries, we
can potentially overcome some of the limitations of other battery types and achieve more
efficient and sustainable energy storage.

38

Fig 2-1 energy density for various types of batteries. [3]The research presented in this thesis aims to design and test a new type of electrocatalyst for
use in Li-air batteries.[4] Li-air batteries are a promising energy storage technology with a hightheoretical energy density, making them ideal for use in electric vehicles and other applications.
The designed material must exhibit both ORR (oxygen reduction reaction) and OER (oxygen
evolution reaction) activities simultaneously. ORR is the process in which oxygen receives
electrons to form water or LixOy,[5] while OER is the opposite process in which water or LixOy
is split into oxygen and electrons. Both of these reactions are crucial for the proper functioningof a Li-air battery. In the case of Li-air batteries, an efficient catalyst is crucial for achieving
high energy density and long cycle life. Therefore, the research presented in this thesis focuses
on designing that exhibits high ORR and OER activity at the same time, with the goal ofenhancing the performance of Li-air batteries. This research has important implications for thedevelopment of more efficient and sustainable energy storage technologies.

39

2.3.

Materials Synthesis

The materials chosen for electrocatalyst synthesis in this thesis to enhance the performance ofLi-air batteries are based on carbon and precious metals. Acetylene Black was selected for its
excellent electrical conductivity, high surface area and high density of functional groups whenoxidated. While Pt and Ir were chosen for their high catalytic activity towards the ORR and
OER, respectively. The combination of these materials is expected to result in a electrocatalyst
that exhibits both ORR and OER activities simultaneously, which is crucial for the proper
functioning of a Li-air battery. This research has important implications for the developmentof more efficient and sustainable energy storage technologies.

40

Table 2-1 Reagent
Perchloric acid

60 %Kanto Chemical Co.

LiTFSI (Lithium bis[trifluoro
methanesulfonyl]imide)>98.0 %

Kanto Chemical Co.

TEGDME (Tetraethyleneglycol ≥99 %dimethyl ether)Sigma-Aldrich

Methanol

99.8 %

Kanto Chemical Co.

Acetone99.0 %

Kanto Chemical Co.

Hexane96.0 %

FUJIFILM Wako
Chemical Co.

Pure

2-propanol

98.0 %

FUJIFILM Wako
Chemical Co.

Pure

5% Nafion DispersionTM

DE521 CS タイプ

FUJIFILM Wako
Chemical Co.

Pure

Acetylene black

2.2 g/cm3 (20 °C)

MERCKChloroplatinic acid97.0+ %

FUJIFILM Wako
Chemical Co.

Chloroiridic acid97.0+ %

Sigma-Aldrich

Sulfuric acid95 %FUJIFILM Wako
Chemical Co.

Pure

Nitric acid

60 %FUJIFILM Wako
Chemical Co.

Pure

LiI(Lithium iodide)97.0+ %

FUJIFILM Wako
Chemical Co.

Pure

LiTFSI (Lithium bis [trifluoro >98.0 %methanesulfonyl] imide)

Kanto Chemical Co.

TEGDME (Tetraethyleneglycol ≥99 %dimethyl ether)Sigma-Aldrich

41

Pure

Table 2-2 Instrumentation

Ultrasonic cleaning machineElectrochemical
stationUT-106SHARP Co.

analyser VSP Potentiostat

Bio-logic Science
Instruments

Rotating ring disk electrode RRDE-3A
deviceBAS

Magnetic stirrer

CT-1AN

AS ONE

Vacuum glove box

UN-650F

UNICO

42

2.3.1. AB Carbon
Acetylene Black, a widely used was type of carbon black in various industrial processes, serves
as an essential basic material in battery systems as conductive additive. The generic structureof Acetylene Black is shown in Figure 2-2. Additionally, it contains oxygen-containinghydrophilic functional groups, due to structural defects based on sp3 carbon.
The research presented in this thesis focuses on designing a material that exhibits high ORR
and OER activity, with the goal of enhancing the performance of Li-air batteries.

Fig 2-2 The generic structure of carbon black.

43

2.3.2. FAB carbon and preparation
For this study, Functional Acetylene Black (FAB) was selected as the carbon support material.
However, before it could be used, Acetylene Black (AB) needed to be modified to introducefunctional groups into the system.
Functional Acetylene Black (FAB) is a derivative of AB that is produced through a process
known as acid corrosion. This process introduces functional groups such as -OH and -COOH
onto the surface of the AB particles, which can improve their compatibility with other materials
and enhance their performance in certain applications.
One key difference between AB and FAB is their diffusivity in water. AB has a relatively highdiffusivity due to its highly porous structure, which allows water to penetrate and move throughthe material easily but it all most cannot disperse in water. In contrast, FAB has a higher
diffusivity in water due to the presence of functional groups on its surface, which can interact
with water molecules.

The synthesis of Functional Acetylene Black (FAB) involved several steps. Firstly, a mixed
acid was prepared by combining H2SO4 and HNO3 with water. Then, 1000 mg of Acetylene
Black (AB) was mixed with the mixed acid and subjected to ultrasonic irradiation for varying
lengths of time (60, or 180 minutes). During this process, the AB particles were dispersed andreacted with the mixed acid to introduce -COOH functional groups onto the surface of theresulting FAB.
The amount of -COOH functional groups in the FAB could be controlled by adjusting thereaction time. Specifically, samples synthesized under 60, and 180 minutes of reaction time
were produced with varying amounts of -COOH functional groups. The resulting FAB samples
were then thoroughly washed with deionized water and vacuum-dried at room temperature forover 12 hours. Table 2-3 displays the FAB samples that were synthesized for this study, alongwith the specific reaction time used to produce each sample.

44

Table 2-3 FAB carbon
Sample name

Reaction time

FAB-6060min

FAB-180

180minThe synthesized FAB samples were intended for use as a substrate for metals deposition. The
introduction of -COOH functional groups onto the surface of FAB is expected to enhance its
compatibility with metal ions and improve the efficiency of metals deposition.

45

2.3.3. Pt Carbon
Pt/C catalyst is widely used in electrochemical applications, particularly in fuel cell
technologies. Some examples of fuel cell vehicles that use Pt/C catalyst include the Toyota
Mirai and Honda Clarity. These vehicles rely on fuel cell technology to generate electricity,and the Pt/C catalyst plays a critical role in facilitating the electrochemical reactions that
produce this electricity.
In this study, Pt/C played a key role in comparing the performance of different types of Pt
including catalysts in an air battery system. Specifically, the study aimed to assess theperformance of catalysts with single metal or composite metals. The objective was to identify
alternative catalyst materials that could potentially offer comparable or improved performancefor use in electrochemical applications, particularly in air battery systems. By using Pt/C as abenchmark catalyst, the study sought to evaluate the performance of novel Pt including
composite metal-based catalyst materials.
The synthesis of Pt metal catalyst (FAB180-Pt 10%) was carried out as follows: to perform
metal deposition onto the FAB-180 carbon support, a 300 ml two-necked flask was chosen as
the reaction container. A solution was prepared by mixing 100 mg of FAB and 100 ml ofethylene glycol, which was subjected to ultrasonic irradiation for 1 hour. A 100 ml dropping
funnel was connected to the side neck of the flask, and a condenser was attached to the mainneck. Next, a metal salt solution containing 6.9 ml 0.01 M H2PtCl6·xH2O mixed with 40 ml ofethylene glycol was added to the dropping funnel. The flask was then immersed in an oil bath,and the temperature was maintained at 150℃ for 12 hours. During the heating process, theswitch of the constant pressure funnel was opened, and the metal salt solution was added
dropwise into the flask. After heating, the solid part was thoroughly washed with deionizedwater and then vacuum-dried at 80℃ for 12 hours. Tiled of FAB180-Pt 10% was 109 mg.
Table 2-4 FAB180-Pt10% catalyst
CarbonStanders

Pt &Weight Percent

FAB-180

6.9 ml@12.5 mg@100mg10%wt

FAB180-Pt 10%

Designed Metal
Weight Percent

10% wt46

Amount109 mg2.3.4. Pt/Ir Carbon
The Pt/Ir catalyst is a type of composite metal-based electrochemical catalyst. The fundamental
idea behind using composite metal cores is to retain two or more physical and chemical
properties simultaneously. In the case of the Pt/Ir catalyst, the combination of platinum andiridium allows the catalyst to exhibit both ORR and OER catalytic activity.
This type of composite metal-based catalyst is particularly useful in electrochemical reactions,where the presence of both metals enhances the performance of the catalyst. For this reason,
the Pt/Ir catalyst is designed to hold both ORR and OER activity simultaneously. Therefore, a
Pt and Ir alloy has been proposed and systematically tested as a composite metalelectrochemical catalyst.
The synthesis of FAB60-Pt/Ir 1:1 was carried out as follows: to perform metal deposition
onto the FAB-60 carbon support, a 300 ml two-necked flask was chosen as the reaction
container. A solution was prepared by mixing 100 mg of FAB-60 and 100 ml of ethylene glycol,
which was subjected to ultrasonic irradiation for 1 hour. A 100 ml dropping funnel wasconnected to the side neck of the flask, and a condenser was attached to the main neck. Next,a metal salt solution containing 6.9ml 0.01 M H2PtCl6·xH2O and 6.9 ml H2IrCl6·xH2O mixed
with 40 ml of ethylene glycol was added to the dropping funnel. The flask was then immersed
in an oil bath, and the temperature was maintained at 150℃ for 12 hours. During the heatingprocess, the switch of the constant pressure funnel was opened, and the metal salt solution wasadded dropwise into the flask. After heating, the solid part was thoroughly washed with
deionized water and then vacuum-dried at 80℃ for 12 hours. Tiled of was 121 mg.
The synthesis of FAB60-Pt/Ir 2:1 was carried out as follows: to perform metal deposition
onto the FAB-60 carbon support, a 300 ml two-necked flask was chosen as the reaction
container. A solution was prepared by mixing 100 mg of FAB-60 and 100 ml of ethylene glycol,
which was subjected to ultrasonic irradiation for 1 hour. A 100 ml dropping funnel wasconnected to the side neck of the flask, and a condenser was attached to the main neck. Next,a metal salt solution containing 9.2 ml 0.01 M H2PtCl6·xH2O and 4.6 ml H2IrCl6·xH2O mixed
with 40 ml of ethylene glycol was added to the dropping funnel. The flask was then immersed
in an oil bath, and the temperature was maintained at 150℃ for 12 hours. During the heatingprocess, the switch of the constant pressure funnel was opened, and the metal salt solution wasadded dropwise into the flask. After heating, the solid part was thoroughly washed with
deionized water and then vacuum-dried at 80℃ for 12 hours. Tiled of was 117 mg.
47

The synthesis of FAB180-Pt/Ir 1:1 was carried out as follows: to perform metal deposition
onto the FAB-180 carbon support, a 300 ml two-necked flask was chosen as the reaction
container. A solution was prepared by mixing 100 mg of FAB-180 and 100 ml of ethylene
glycol, which was subjected to ultrasonic irradiation for 1 hour. A 100 ml dropping funnel wasconnected to the side neck of the flask, and a condenser was attached to the main neck. Next,a metal salt solution containing 6.9ml 0.01 M H2PtCl6·xH2O and 6.9 ml H2IrCl6·xH2O mixed
with 40 ml of ethylene glycol was added to the dropping funnel. The flask was then immersed
in an oil bath, and the temperature was maintained at 150℃ for 12 hours. During the heatingprocess, the switch of the constant pressure funnel was opened, and the metal salt solution wasadded dropwise into the flask. After heating, the solid part was thoroughly washed with
deionized water and then vacuum-dried at 80℃ for 12 hours. Tiled of 119 mg.
The synthesis of FAB180-Pt/Ir 2:1 was carried out as follows: to perform metal deposition
onto the FAB-180 carbon support, a 300 ml two-necked flask was chosen as the reaction
container. A solution was prepared by mixing 100 mg of FAB-180 and 100 ml of ethylene
glycol, which was subjected to ultrasonic irradiation for 1 hour. A 100 ml dropping funnel wasconnected to the side neck of the flask, and a condenser was attached to the main neck. Next,a metal salt solution containing 9.2 ml 0.01 M H2PtCl6·xH2O and 4.6 ml H2IrCl6·xH2O mixed
with 40 ml of ethylene glycol was added to the dropping funnel. The flask was then immersed
in an oil bath, and the temperature was maintained at 150℃ for 12 hours. During the heatingprocess, the switch of the constant pressure funnel was opened, and the metal salt solution wasadded dropwise into the flask. After heating, the solid part was thoroughly washed with
deionized water and then vacuum-dried at 80℃ for 12 hours. Tiled of was 119 mg.

48

Table 2-5 FAB(x)-Pt/Ir catalysts
CarbonPt &Ir &Designed Metal

Standers

Weight Percent

Weight Percent

Weight Percent

FAB-606.9 ml @6.9 ml @@12.5 mg12.5 mg

100 mg

10%wt

10%wt

FAB-609.2 ml @4.6 ml @@16.7 mg

8.3 mg

100 mg

10%wt

10%wt

FBA-180

6.9 ml @6.9 ml @@12.5 mg12.5 mg

100 mg

10%wt

10%wt

FAB-180

9.2 ml @4.6 ml @@16.7 mg

8.3 mg

100 mg

10%wt

10%wt

Yield

FAB6020%wt

121 mg20%wt

117 mg20%wt

119 mg20%wt

119 mgPt/Ir 1:1

FAB60Pt/Ir 2:1

FAB180Pt/Ir 1:1

FAB180Pt/Ir 2:1

49

2.4.

Analysis and Discussion

This section focuses on the use of TGM, SEM-EDS, TEM, and XPS to analyse the structuresof the AB carbon material and the FAB(x)-Pt/Ir catalysts. The aim is to identify and discuss
the structural aspects of materials.

2.4.1. SEM-SED
SEM-EDS (Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy) is a
powerful technique used to identify and quantify the elemental composition of materials. By
analyzing the characteristic X-rays emitted from the sample, the technique can provide valuable
information about the spatial distribution and concentration of various elements. In this study,
SEM-EDS was employed to investigate the elemental composition of obtained carbon
materials.
SEM-EDS was utilized to conduct elemental analysis on AB, FAB, FAB-Pt, and FAB-Pt/Ir
materials. Table 2-6 presents the weight percentage of C, O, Pt, and Ir for each material.
Table 2-6 The weight percentage of rations elements in catalysts by SEM-EDS
Element Weight (percent)
Sample
C

O

Pt

Ir

Metal Total (%)

AB

96.29

3.71

-

-

FAB-60

93.47

6.53

-

-

FAB-180

88.95

11.05

-

-

FAB180-Pt10%

84.62

6.65

8.73

-

8.73

FAB60-Pt/Ir 1:1

75.77

4.43

8.61

11.63

20.24

FAB60-Pt/Ir 2:1

76.13

7.25

11.59

5.03

16.62

FAB180-Pt/Ir 1:1

78.07

3.96

9.04

8.92

17.96

FAB180-Pt/Ir 2:1

77.01

5.09

12.91

4.99

17.90

As for AB carbon, the percentage of oxygen increased from 3.71% to 6.53% in FAB-60 and to
11.05% in FAB-180 after reaction. This increase in oxygen percentage suggests that functionalgroups were introduced into the carbon material, altering its surface structure. The results
50

demonstrate that the AB carbon underwent significant changes in surface after reaction, which
could have important implications for its electrochemical performance.
In the case of FAB180-Pt10%, the presence of 8.73% Pt in the catalyst led to a decrease inoxygen content to 6.65%. This reduction in oxygen content indicates disapperance of some CO bonds.
The FAB(x)-Pt/Ir catalysts are the main focus of present study. The elemental analysis of metalcomposites of FAB-60 and FAB-180 carbons revealed that the oxygen percentage in FAB-60Pt/Ir was higher than in FAB-180-Pt/Ir, regardless of the metal percentage, which can explain
the difference in functional group percentage between the two carbons. The study then focusedon the metal component of the catalysts, where the weight ratio of Pt/Ir was either 2:1 or 1:1.
It was found that the oxygen weight percent was higher when the Pt/Ir weight ratio was 2:1,
compared to 1:1. This observation can be further investigated with TEM and XPS data, which
provide information about the morphology, size distribution, and chemical state of the catalyst
particles.
Understanding how metal percentage and weight load affect the oxygen percentage andfunctional group distribution in carbon can lead to the development of more efficient catalystmaterials. In this work, the oxygen percentage and functional group distribution in FAB carbon
were modified, leading to changes in the structure and surface of Pt and Ir. This was confirmed
through clear data obtained from TEM and XPS analyses.

51

Fig. 2.4 SEM images of FAB-60 and FAB-180

Fig. 3-5 SEM images of FAB- FAB(x)-Pt/Ir52

2.4.2. TGA
Thermogravimetric analysis (TGA) is a technique used in materials science and chemistry toanalyze the thermal stability and composition of a sample by measuring its weight changes asa function of temperature or time.
TGA is being used to calibrate the weight with metal in the FAB180-Pt/Ir 2:1 catalyst. The
weight percent of Pt and Ir alloy in the catalyst is then compared with the data obtained fromscanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), as
shown in part 2.4.2.
The data in Figure 2-4 indicates that the weight percent of Pt and Ir alloy in the FAB180-Pt/Ir
2:1 catalyst is 18.95%, which is consistent with the results obtained from SEM-EDS.
Overall, TGA is a valuable tool for analyzing the thermal properties and composition ofmaterials and can provide important insights into their characteristics and performance.

Fig 2-6 TGM for FAB180- Pt/Ir 2:1

53

2.4.3. TEM
After SEM-EDS, TEM was measured to check nano-particles sizes and structure. TEM imageis shown in Figure 2-7.
In addition to the nano-particle size, the distribution of nanoparticles within the carbon material
also plays a crucial role in the oxygen content of the catalyst. It was found that in FAB-180based catalysts with a large number of functional groups, the metal nanoparticles could be
distributed more uniformly within the carbon material. This is due to the fact that the functionalgroups provide more surface area and sites for the metal particles to attach to, leading to a moreeven distribution.
The catalysts were analyzed through selected area electron diffraction (SAED) pattern analysis,
revealing that the metal nanoparticles containing Pt and Ir were oriented with Pt(111) andIr(111), respectively. This was further confirmed through high-resolution transmission electron
microscopy (HRTEM) images, which showed distinct variations between the various catalysts.
In comparison to FAB-60-based catalysts, the FAB-180-based catalysts exhibited a complete
lattice structure, while it was challenging to obtain reliable crystal phase information for the
FAB-60-based catalysts. Finally, the HAADF image of FAB180-Pt/Ir 1:1 was obtained,
displaying the corresponding component mapping of Pt and Ir elements. As per the HAADF
image, it was observed that Pt and Ir remained alloyed in the catalyst.
TEM images showed desired materials with uniform loading of metal nanoparticle on FAB
was successfully prepared. Further, alloyed bimetallic structure and orientation of Pt/Ir was
also clarified.

54

Table 2-7 Nano metal particles size in catalysts.

SampleMean/nmDistr./nm

Freq.

FAB180-Pt10%

4.75

5-5.4

27.78%

FAB60-Pt/Ir 1:1

2.61

2.5-2.8

37.50%

FAB60-Pt/Ir 2:1

3.07

2.8-3.1

35.00%

FAB180-Pt/Ir 1:1

2.06

1.9-2.2

30.36%

FAB180-Pt/Ir 2:1

2.39

2.2-2.6

35.00%

55

Fig

20nm

20nm

FAB60-Pt/Ir 2:1

FAB180-Pt/Ir 1:1

56

57

58

Fig 2-7 TEM image with catalyst: SAED patterns, (a) FAB60-Pt/Ir 1:1, (b) FAB180-Pt/Ir 1:1;
HAADF-STEM image, (c) FAB60-Pt/Ir 1:1, (d) FAB180-Pt/Ir 1:1; HR-TEM image (e) FAB180Pt/Ir 1:1 and EDS elemental mapping images (f) FAB180-Pt/Ir 1:1.
59

2.4.4. XPS
The analysis of X-ray photoelectron spectroscopy (XPS) data revealed notable differences
between the AB carbon before and after the oxidation. Initially, the main O 1s peak was
observed at 533 eV with a weak peak at 528.7 eV. However, after 60 minutes of reaction, themain peak shifted to 533.3 eV and the weak peak shifted to 531.7 eV with the same peak area.
After 180 minutes of oxidation, further peak shift did not occur, but the peak area of C=O was
doubled compared to that of C-O. The C-C peak in C 1s spectrum of in AB carbon was initiallyobserved at 284.5 eV. However, after the oxidation, the peak area shifted slightly to lower
energy region, FAB-60 at 284.2 eV, FAB-180 at 284.0 eV. Similarly, in the spectral O 1s
spectrum, the C=O peak shifted to lower energy region and was observed at 288.5 eV in FAB180 compared to 289.0 eV in FAB-60. The peak area also changed, and the C-O and C=O
peaks became larger in FABs than in AB. These changes suggest that more functional groups
were added in the carbon structure after the oxidation.

60

Fig 2-8 XPS with carbon standers

When analyzing the C 1s spectrum of the catalysts, it was observed that the C=O peak
disappeared after introducing the metal. The O 1s peak showed a shift to the left, with raw
intensities of 531.9 eV and 532.1 eV for the FAB-60 and FAB-180 based catalysts, respectively.
61

Interestingly, both of these carbon-based catalysts showed the same peak shift as the metal
weight changed. The only exception was the Pt/Ir 2:1 catalyst, which had a very weak signal.
Further analysis revealed that the Pt-O/Organic C-O peak in the FAB60-Pt/Ir 1:1 and FAB180Pt/Ir 1:1 catalysts were located at 531.0 eV, while in the FAB60-Pt/Ir 2:1 and FAB180-Pt/Ir
2:1 catalysts, they were located at 531.5 eV. These results suggest that the presence of Pt and
Ir in the catalysts plays a crucial role in the changes observed in the C and O spectra. It is clearthat the type and weight of the metals used in the catalysts affect the chemical environment of
the carbon structure, which may have implications for the catalytic activity and selectivity ofthese materials in electrocatalysis.

62Raw Intensity
Peak Sum
Background
C-C/C-metal
C=C
C-O
C=O

150000100000

Raw Intensity
Peak Sum
BackgroundPt-O/Organic C-O
Organic C=O
-O-H
C-O

42000

C1s

40000
38000

Raw Intensity

Raw Intensity

200000

50000

36000

O1s

34000
32000
30000
28000

0

26000
24000

292

290

288

286

284

282

540

538

536

534

B.E.(eV)

532

530

528

526

B.E.(eV)

FAB-60 Pt:Ir 1:1

200000180000

Raw Intensity

160000140000120000100000

C1s

80000

48000

Raw Intensity
Peak Sum
BackgroundPt-O/Organic C-O
Organic C=O
-O-H
C-O

46000
44000

Raw Intensity

Raw Intensity
Peak Sum
Background
C-C/C-metal
C=C
C-O
C=O

42000
40000
38000

O1s

36000
34000

60000
40000

32000

20000

30000

0
294

292

290

288

286

284

282

28000
538

280

536

534

532

530

528

B.E.(eV)B.E.(eV)

FAB-60 Pt:Ir 2:1

150000100000C1s

Raw Intensity
Peak Sum
Background
C-C/C-metal
C=C
C-O
C=O

45000

Raw Intensity

Raw Intensity

200000

40000

30000

0

25000

290

288

286

284

540

282

O1s

35000

50000

292

Raw Intensity
Peak Sum
BackgroundPt-O/Organic C-O
Organic C=O
-O-H
C-O

538

536

534

B.E.(eV)B.E.(eV)

FAB-180 Pt:Ir 1:1

63

532

530

528

48000200000C1s

180000140000120000100000
80000

44000

Raw Intensity

160000

Raw Intensity

46000

Raw Intensity
Peak Sum
Background
C-C/C-metal
C=C
C-O
C=O

60000

42000

Raw Intensity
Peak Sum
BackgroundPt-O/Organic C-O
Organic C=O
-O-H
C-O

O1s

40000
38000
36000
34000

40000
32000

20000
30000

0
294

292

290

288

286

284

282

28000
538

280

536

534

B.E.(eV)

532

530

528

B.E.(eV)

FAB-180 Pt:Ir 2:1
Fig 2-9 XPS with catalyst on C1s and O1s

Further analysis of the data revealed some interesting trends. The Pt peaks of Pt 7/2 in the
FAB60-Pt/Ir 1:1 and FAB60-Pt/Ir 2:1 catalysts were located at 71.20 eV and 71.19 eV,
respectively, while in the FAB180-Pt/Ir 1:1 and FAB180-Pt/Ir 2:1 catalysts, they were locatedat 71.13 eV and 71.03 eV. Similarly, the Pt 2+ peaks in the FAB60-Pt/Ir 1:1 and FAB60-Pt/Ir
2:1 catalysts were located at 72.35 eV and 72.34 eV, respectively, while in the FAB180-Pt/Ir
1:1 and FAB180-Pt/Ir 2:1 catalysts, they were located at 72.28 eV and 72.18 eV. It wasobserved that all Pt peaks in the FAB-60 based catalysts shifted to higher binding energy region
when compared to those in the FAB-180 based catalysts.
Further analysis also revealed that the Ir peaks of Ir 7/2 in the FAB180-Pt/Ir 1:1 and FAB60Pt/Ir 1:1 catalysts were located at 60.41 eV and 60.60 eV, respectively, while in the FAB180Pt/Ir 2:1 and FAB60-Pt/Ir 2:1 catalysts, they were located at 60.65 eV and 60.63 eV. The peaksof Ir 4+ in the FAB180-Pt/Ir 1:1 and FAB60-Pt/Ir 1:1 catalysts were located at 61.51 eV and
61.70 eV, respectively, while in the FAB180-Pt/Ir 2:1 and FAB60-Pt/Ir 1:1 catalysts, they werelocated at 61.75 eV and 58.73 eV. It was observed that the Ir peaks in the FAB-180 based
catalysts shifted to lower banding energy region compared to those in the FAB-60 based
catalysts under Pt:Ir ratio of 1:1 loading. However, when the Pt:Ir loading was changed to 2:1,
the data was almost the same.
The peak area between Ir 7/2 and Ir 4+ (7/2) revealed that when Pt:Ir was loaded in a 1:1 ratio,
the FAB60-Pt/Ir 1:1 catalyst had 40.9% of Ir 7/2 and 7.3% of Ir 4+, while FAB180-Pt/Ir 1:1
had 16.5% of Ir 7/2 and 37.3% of Ir 4+. This suggests that in FAB180-Pt/Ir 1:1, the Ir was64

predominantly loaded as IrO2, while in FAB60-Pt/Ir 1:1, the Ir was predominantly loaded as Ir
metal.

pt 4f.txt
22

Pt 4f

20

Name
Pt 4f 7/2
Pt f4 5/2
Pt 4f 2+ 7/2
Pt 4f 2+ 5/2
Pt 4f 4+ 7/2
Pt 4f 4+ 5/2

18

Pos. Offset FWHM
L.Sh.
71.20 0.00 1.20 LA(1.2,85,70)
74.53 3.33 1.20 LA(1.2,85,70)
72.35 1.15 0.40
GL(70)
75.68 4.48 0.40
GL(70)
74.15 2.95 0.54
GL(70)
77.48 6.28 0.54
GL(70)Area%Area
23976.44 56.96
17982.33 42.72
0.00
0.00
0.00
0.00
75.08
0.18
56.31
0.13

CPS x 10-3

16

14

12

10

8

84

80

76
Binding Energy (eV)72

Fig 2-10 Peaks of Pt 4f for FAB60 Pt:Ir 1:1

65

68

pt 4f.txt
Residual STD = 3.224
40

Pt 4f

35
Name
Pt 4f 7/2
Pt 4f 5/2
Pt 4f 2+ 7/2
Pt 4f 2+ 5/2
Pt 4f 4+ 7/2
Pt 4f 4+ 5/2

Pos. Offset FWHM
L.Sh.
71.19 0.00 1.22 LA(1.2,85,70)
74.52 3.33 1.22 LA(1.2,85,70)
72.34 1.15 2.65
GL(70)
75.67 4.48 2.65
GL(70)
74.14 2.95 1.01
GL(70)
77.47 6.28 1.01
GL(70)

Area%Area
54167.97 51.02
40625.97 38.27
5205.374.90
3904.033.68
1291.111.22
968.330.91

30

CPS x 10-3

Pt 4f 7/2

25

20

15

Pt 4f 4+ 5/2
Pt 4f 4+ 7/2

10

84

80

76
Binding Energy (eV)Fig 2-11 Peaks of Pt 4f for FAB60 Pt:Ir 2:1

66

72

pt 4f.txt

Pt 4f
20

18

Name
Pt 4f 7/2
Pt f4 5/2
Pt 4f 2+ 7/2
Pt 4f 2+ 5/2
Pt 4f 4+ 7/2
Pt 4f 4+ 5/2

Pos. Offset FWHM
L.Sh.
71.13 0.00 1.23 LA(1.2,85,70)
74.46 3.33 1.23 LA(1.2,85,70)
72.28 1.15 2.51
GL(70)
75.61 4.48 2.51
GL(70)
74.08 2.95 1.44
GL(70)
77.41 6.28 1.44
GL(70)

Area%Area
25986.88 53.01
19490.16 39.76
1617.663.30
1213.25
2.47
409.190.83
306.890.63

CPS x 10-3

16

14

12

10

8

6

84

80

76
Binding Energy (eV)Fig 2-12 Peaks of Pt 4f for FAB180 Pt:Ir 1:1

67

72

pt 4f.txt

30

CPS x 10-3

25

Pt 4f

Name
Pt 4f 7/2
Pt f4 5/2
Pt 4f 2+ 7/2
Pt 4f 2+ 5/2
Pt 4f 4+ 7/2
Pt 4f 4+ 5/2

Pos. Offset FWHM
L.Sh.
71.03 0.00 1.23 LA(1.2,85,70)
74.36 3.33 1.23 LA(1.2,85,70)
72.18 1.15 9.27
GL(70)
75.51 4.48 9.27
GL(70)
73.98 2.95 1.79
GL(70)
77.31 6.28 1.79
GL(70)Area%Area
39902.78 55.89
29927.08 41.92
0.00
0.00
0.00
0.00
894.91
1.25
671.18
0.94

20

15

10

84

80

76
Binding Energy (eV)

68

72

68

Intensity (a.u.)

Pt 4f 7/2
Pt f4 5/2
Pt f4 2+ 7/2
Pt 4f 2+ 5/2
Pt 4f 4+ 7/2
Pt 4f 4+ 5/2

80

78

76

74

72

Binding energy (eV)Fig 2-13 Peaks of Pt 4f for FAB180 Pt:Ir 1:1

69

70

40000

Pt 4f
35000

FAB180Pt:Ir1:1
FAB60Pt:Ir1:1
FAB180Pt:Ir2:1
FAB60Pt:Ir2:1

CPS

30000
25000
20000
15000
10000
5000
82

80

78

76

74

72

70

68

EB (eV)Fig 2-14 XPS with catalyst on Pt 4f

Table 2-8 Pt 4f peaks shifts (eV)
FAB180FAB60

FAB180

FAB60

Pt:Ir 1:1

Pt:Ir 1:1

Pt:Ir 2:1

Pt:Ir 2:1

Pt 7/2

71.13

71.20

71.03

71.19

Pt 2+

72.28

72.35

72.18

72.34

Pt 4+

74.08

74.15

73.98

74.14

70

ir f4.txt

25
Residual STD = 3.595

Ir 4f

20

Name
Ir 4f7/2
Ir 4f5/2
Ir 4+ 4f7/2
Ir 4+ 4f5/2
Ir 2+ 4f7/2
Ir 2+ 4f5/2

Pos. Offset FWHM
L.Sh.
60.60 0.00 1.25 LA(1.2,85,70)
63.53 2.93 1.25 LA(1.2,85,70)
61.70 1.10 2.62
GL(70)
64.63 4.03 2.62
GL(70)
61.40 0.80 1.60
GL(70)
64.33 3.73 1.60
GL(70)

Area%Area
27718.19 40.90
20788.64 30.68
4974.427.34
3730.815.51
6032.338.90
4524.25
6.68

CPS x 10-3

15
Ir 4f7/2
Ir 4f5/2

10

Ir 4+
5

69

66

63
Binding Energy (eV)Fig 2-15 Peaks of Ir 4f for FAB60 Pt:Ir 1:1

71

60

57

ir 4f.txt
Residual STD = 4.093

Ir 4f

40

35

Name
Ir 4f7/2
Ir 4f5/2
Ir 4+ 4f7/2
Ir 4+ 4f5/2
Ir 2+ 4f7/2
Ir 2+ 4f5/2

Pos. Offset FWHM
L.Sh.
60.63 0.00 0.84 LA(1.2,85,70)
63.56 2.93 0.84 LA(1.2,85,70)
61.73 1.10 1.81
GL(70)
64.66 4.03 1.81
GL(70)
61.43 0.80 1.31
GL(70)
64.36 3.73 1.31
GL(70)Area%Area
4115.10 10.46
3086.32
7.85
14579.10 37.07
10934.32 27.80
3777.999.61
2833.50
7.21

CPS x 10-3

30

25

20

15

Ir 4+
10

Ir 4f5/2
Ir 4f7/2
5

72

69

66
Binding Energy (eV)63

Fig 2-16 Peaks of Ir 4f for FAB60 Pt:Ir 2:1

7260

ir 4f.txt
22

Residual STD = 4.412

Ir 4f

20

18

16

Name
Ir 4f7/2
Ir 4f5/2
Ir 4+ 4f7/2
Ir 4+ 4f5/2
Ir 2+ 4f7/2
Ir 2+ 4f5/2

Pos. Offset FWHM
L.Sh.
60.41 0.00 0.89 LA(1.2,85,70)
63.34 2.93 0.89 LA(1.2,85,70)
61.51 1.10 1.89
GL(70)
64.44 4.03 1.89
GL(70)
61.21 0.80 0.77
GL(70)
64.14 3.73 0.77
GL(70)

Area%Area
5387.56 16.49
4040.67 12.37
12174.44 37.27
9130.83 27.95
1102.473.38
826.85
2.53

CPS x 10-3

14

12

10

Ir 4+

8

Ir 4f5/2
6
Ir 4f7/2

4

2
72

69

66
Binding Energy (eV)

73

63

60

Intensity (a.u.)

Ir 4f 7/2
Ir 4f 5/2
Ir 4+ 7/2
Ir 4+ 5/2
Ir 2+ 7/2
Ir 2+ 5/2

68

66

64

62

60

Binding energy (eV)Fig 2-17 Peaks of Ir 4f for FAB180 Pt:Ir 1:1

74

58

ir 4f.txt
Residual STD = 3.903

Ir 4f

30

25

Name
Ir 4f7/2
Ir 4f5/2
Ir 4+ 4f7/2
Ir 4+ 4f5/2
Ir 2+ 4f7/2
Ir 2+ 4f5/2

Pos. Offset FWHM
L.Sh.
60.65 0.00 1.05 LA(1.2,85,70)
63.58 2.93 1.05 LA(1.2,85,70)
61.75 1.10 1.97
GL(70)
64.68 4.03 1.97
GL(70)
61.45 0.80 1.16
GL(70)
64.38 3.73 1.16
GL(70)

Area%Area
11063.25 21.82
8297.44 16.36
13790.38 27.20
10342.78 20.40
4121.028.13
3090.76
6.10

CPS x 10-3

20

15

Ir 4+
10
Ir 4f5/2
Ir 4f7/2

5

69

66

63

60

Binding Energy (eV)Fig 2-18 Peaks of Ir 4f for FAB180 Pt:Ir 2:1

Table 2-9 Ir 4f peaks shifts (eV)
FAB180FAB60

FAB180

FAB60

Pt:Ir 1:1

Pt:Ir 1:1

Pt:Ir 2:1

Pt:Ir 2:1

Ir 7/2

60.41

60.60

60.65

60.63

Ir 4+

61.51

61.70

61.75

61.73

Ir 2+

61.21

61.40

61.45

61.48

75

57

2.5.

Conclusion

In this study, two carbon based materials for bi-functionalized catalysts were obtained byvarying the reaction time for oxidation of AB carbon: FAB-60 and FAB-180, which havedifferent oxygen contents and physical and chemical properties were prepared. Four types ofelectrochemical catalysts were designed, synthesized, and tested by controlling the weightpercent of the metals loaded on carbon materials. The microstructure of the FAB(x)-Pt/Irfamily catalysts was found to be influenced by the functional groups present in the carbon andthe weight percent of the metal. If the carbon has sufficient functional groups for metal bonding,the size of the nanoparticles can be controlled to be uniform and in the nanoscale range.

76

References[1] Aravindan, V., Gnanaraj, J., Lee, Y. S., & Madhavi, S. (2013). Journal of Materials ChemistryA, 1(11), 3518-3539.
[2] NASA GISS Surface Temperature Analysis (v4), <https://data.giss.nasa.gov/gistemp/graphs_v4/>,(2019).
[3] Christensen, L., Fischer, N., Kroffke, S., Lemburg, J., & Ahlers, R. (2011). Cost-effective
autonomous robots for ballast water tank inspection. Journal of ship production and design, 27(3),127.
[4] Kraytsberg, A., & Ein-Eli, Y. (2011). Review on Li–air batteries—Opportunities, limitations andperspective. Journal of Power sources, 196(3), 886-893.
[5] Peng, Z., Freunberger, S. A., Hardwick, L. J., Chen, Y., Giordani, V., Bardé, F., ... & Bruce, P. G.
(2011). Oxygen reactions in a non‐aqueous Li+ electrolyte. Angewandte Chemie International
Edition, 50(28), 6351-6355

77

3. Chapter 3
A series of FAB(x)-Pt/Ir catalysts for Li-air battery

3.1.

Abstract

Despite extensive research on secondary batteries for improving electrochemical performance,
the key factor in metal-air batteries is the control of oxygen reduction reaction (ORR) andoxygen evolution reaction (OER) activity during charge and discharge cycles. The challenge
is to develop batteries with long lifespan and minimal attenuation. In this study, the FAB(x)Pt/Ir catalyst family will be tested using linear sweep voltammetry (LSV) and cyclic
voltammetry (CV) before full charge-discharge cycles are performed in a Li-air battery, inorder to evaluate the ORR and OER performance.

78

3.2.

Introduction

Based on Figure 3-1, it can be observed that different materials have different energy densities.
Hydrogen and natural gas are capable of storing high energy per unit mass, while metals arecapable of storing high energy per unit volume. It is worth noting that the energy density of amaterial is an important factor in determining its suitability for use in energy storage
applications. For instance, Li-ion batteries have a lower energy density compared to Li-air
batteries, which makes Li-air batteries more attractive for high-energy applications. [1]Similarly, the high energy density of metals makes them promising candidates for use in metalair batteries. Advances in material technology have made it possible to explore the potential of
metal-air batteries as a viable option for high-energy density applications. [2]The development of new materials has made metal-air batteries an exciting area of research in
the field of secondary batteries. These cutting-edge energy devices, such as Li-air batteries,
offer remarkably high energy density values that are comparable to gasoline and about ten
times higher than those of Li-ion batteries. This means that metal-air batteries have the potential
to revolutionize energy storage, especially in applications where weight and space are at apremium, such as in electric vehicles and portable electronics. While there are still somechallenges to overcome, such as improving the durability and stability of these batteries, theprogress that has been made so far is promising. As materials science continues to advance, it
is likely that metal-air batteries will become increasingly efficient, reliable, and cost-effective,
making them a key technology for the future of energy storage. [3]79Fig 3-1 Energy densities plot

The metal-air battery typically consists of three parts: the anode (1), cathode (2), and electrolyte(3). The anode is typically a pure metal. With widely used metals include aluminum (4300
Wh/kg), sodium (1677 Wh/kg), magnesium (2789 Wh/kg), and lithium (5210 Wh/kg).
Electrolytes are available in states: liquid solvent, a mixture of polymer and liquid solvent, andpolymer-based solid etc. [4]Similar to a fuel cell, the cathode in a metal-air battery is where the key reaction takes place.
In a metal-air battery, the cathode needs to maintain activity for OER and ORR for chargedischarge. For this reason, catalyst design needs to follow three main criteria: (1) high ORR
and OER activity at the same time, (2) low overpotential during charge-discharge, and (3) alarge surface area.
Li-air batteries have been considered as one of the most promising next-generation energy storage systems due to their high energy density. However, the development of Li-air batteries has
been limited by several challenges, particularly at the cathode. The cathode is responsible forthe oxygen reduction reaction (ORR) during discharge and the oxygen evolution reaction (OER)
during charging, which are essential for the battery's performance. [5]80In this context, the FAB(x)-Pt/Ir catalysts has shown potential for enhancing the performanceof Li-air batteries. FAB(x)-Pt/Ir catalysts exhibit excellent activity for both the ORR and OER,
which are advantageous for efficient Li-air battery operation. Further analysis has also revealed
that the oxygen percentage and functional group distribution in the carbon can significantly
affect the performance of the catalyst. By understanding the effects of metal percentage andmetal loading factors, we can develop more efficient and effective catalyst materials for Li-air
batteries.

81

3.3.

Materials and Experimental

3.3.1. Catalyst
In this chapter, the focus is on the electrochemical evaluation and charge-discharge
performance of the FAB(x)-Pt/Ir catalyst based cells in LAB. The selection of the catalyst is
crucial as it must exhibit high activity for both the oxygen reduction reaction (ORR) andoxygen evolution reaction (OER) to enable efficient battery operation. The discussion will
provide insights into the performance of the FAB(x)-Pt/Ir catalysts based cells in LAB.

Table 3-1 FAB(x)-Pt/Ir catalysts
Element Weight percent (Follow By
SEM-EDS)
Sample
C

O

Pt

Ir

Metal

Design Metal

Deviation With

Weight Percent

DesignTotal
FAB60-Pt/Ir
1:1
FAB60-Pt/Ir
2:1
FAB180-Pt/Ir
1:1
FAB180-Pt/Ir
2:1

75.77 4.43

8.61

11.63

20.24

20%wt

+1.2%

76.13 7.25 11.59

5.03

16.62

20%wt

-16.9%

78.07 3.96

9.04

8.92

17.96

20%wt

-10.2%

77.01 5.09 12.91

4.99

17.90

20%wt

-10.5%

82

3.3.2. Electrochemical Detection
Electrochemical measurements are essential in determining the activity of cathode materials
for Li-air batteries. In this chapter, the performance of bifunctional Pt/Ir nanoparticles-based
electrodes was evaluated through electrochemical analysis to determine their ORR and OER
activity. The results provide important insights into the efficiency of the FAB(x)-Pt/Ir catalyst
family and their potential use in Li-air batteries. The electrochemical methods impedance
involved cyclic voltammetry (CV), linear sweep voltammetry (LSV), and charge-discharge,
which enabled the determination of various electrochemical parameters such as over potential,
internal resistance, capacity, CE, and charge-discharge stability.

3.3.3. Air-Battery
The positive electrode for the Li-air battery was prepared by coating a Pt-Ir-FAB ink onto
a coated carbon cloth. The ink was made by mixing the FAB-based catalyst with a
polyvinylidene fluoride (PVDF) binder in a 9:1 ratio in N-methyl pyrrolidone (NMP) via
ultrasonication. The cathode was produced using a brush coating technique, and the coatedelectrode was then dried in a vacuum oven at 80°C for 2 hours. Subsequently, the electrodewas hot-pressed at 80°C for 12 hours to obtain a uniform coating. Lastly, 15 mm diameter discs
were punched out to use as the cathode.
The fabrication of the Li-air battery involved the use of the cathode prepared in section 3.3.1,
as shown in Figure 3-2. The Li-air battery was based on a 2025-coin cell, with a bottom capthat had a 1cm hole for oxygen exchange. All coin cell components were kept under an 80℃
vacuum oven for 5 hours after washing with acetone. Glass fiber paper was used as a separator,
which was cut into disks of 18mm diameter, and a 15 mm diameter lithium disk was cut fromlithium foil. The cell was fabricated in an argon Ar gas glove box.
The electrolyte was prepared with 0.1M LiI (Lithium iodide) and 0.1M LiTFSI (Lithium
bis[trifluoro methanesulfonyl] imide) in TEGDME (Tetraethyleneglycol dimethyl ether). The
electrolytes were sufficiently dehydrated via vacuum drying.

83

Fig. 3-2 Construction of Li-air battery

Li-air battery charge- discharge testing was carried under test chamber as shown in Figure
3-3.

Fig. 3-3 schematic diagram of Li-air battery test chamber

Before conducting the Li-air battery charge-discharge tests, the test chamber was purged withoxygen gas to eliminate any moisture or other gas contamination. During the tests, the chamber

84

atmosphere was maintained at 99.9% oxygen, and the pressure was controlled to achieve thedesired level within the chamber. The pressure was monitored every 12 hours to ensure it
remained within the target range which is keep in to 0.1 MPa.

85

3.4.

Analysis and Discussion

This section of the thesis discusses the application of three electrochemical techniques,
impedance, linear sweep voltammetry (LSV), cyclic voltammetry (CV), and charge-discharge,
to investigate the performance of the FAB(x)-Pt/Ir catalysis. The objective is to analyse theiractivity and behaviour among the catalyst materials. Through these analyses, the differences
between the catalysts will be identified and further discussed.

863.4.1. LSV
The LSV analysis was carried out for a comparison of the ORR and OER activities of theFAB(x)-Pt/Ir catalysts, which is important to estimate their potential utility in Li-air batteries.
LSV measurements were carried out under 0.1M HClO4 aq. (perchloric acid). The results ofmeasurements are shown in Figure 3-4.

(Reference Electrode: Ag/AgCl Counter Electrode: Pt Scan speed: 50 mV/sec Gas: Oxygen)
ORR results in 0.1M perchloric acid

(Reference Electrode: Ag/AgCl Counter Electrode: Pt Scan speed: 50 mV/sec Gas: Nitrogen)
OER results in 0.1M perchloric acidFig 3-4 LSV for catalyst
87LSV analysis was performed to determine the onset potential and maximum current of the ORR
for the FAB(x)-Pt/Ir catalysts. The FAB60-Pt/Ir 2:1 catalyst showed an onset potential of
approximately 0.61V, while the FAB180-Pt/Ir 1:1 catalyst exhibited an onset potential ofaround 0.54V. In terms of ORR activity, the FAB180-Pt/Ir 1:1 catalyst demonstrated better
performance than the FAB60-Pt/Ir 2:1 catalyst based on the maximum current value. However,the FAB60-Pt/Ir 2:1 catalyst performed better than the FAB180-Pt/Ir 1:1 catalyst in terms of
the onset potential of the ORR reaction.
From Table 3-2, it can be seen that the OER activity of the FAB180-Pt/Ir 1:1 catalyst (28.21
Ag-1 ) is lower than that of the FAB60-Pt/Ir 2:1 catalyst (36.77 Ag-1), respectively. Additionally,
the overpotential for the FAB60-Pt/Ir 2:1 catalyst is larger (304 mV) compared to that for
FAB180-Pt/Ir 1:1 catalyst (294 mV). While the FAB180-Pt/Ir 1:1 catalyst has lower mass
activity compared to FAB60-Pt/Ir 2:1, it has a lower overpotential, making it easier for the
OER reaction to occur, which is favourable for the discharge process in a Li-air battery.

Table 3-2 OER activity

Catalysts

Loading

Mass activity

Overpotential

Refence(mg cm-2)(A g-1)@ 10 mA cm-2

FAB60-Pt/Ir 2:1

0.0061 (Ir)

36.77

304

This work

FAB180-Pt/Ir 1:1

0.0102 (Ir)

28.21

294

This work

IrO2/CNT

0.076 (Ir)

88

270

[6]

Pt/IrO2

0.3 (Ir)

5

330

[7]

IrO2

0.38 (IrO2)

9.6

282

[8]

IrOx-Ir

0.13 (IrOx-Ir)

8

–

[9]

Ir/Ti4O7

0.033 (Ir)

4.2

-

[9]

Table 3-3 shows OER activity for Ir metal include system. One of important aspect on OER active ismass activity.

The even and discernible crystal phase of FAB180-Pt/Ir 1:1 is likely responsible for the lower

88overpotential observed during OER activity. This may be due to the more uniform distributionof active sites on the catalyst surface, which can facilitate the transfer of reactants and products
during the electrochemical reaction. As a result, FAB180-Pt/Ir 1:1 exhibits a more efficient andstable OER performance, making it a promising candidate for use in Li-air batteries.

893.4.2. CV
The electrochemical measurements were performed under aqueous electrolyte 0.1M HClO4 aq.
(perchloric acid), using a glassy carbon electrode loaded with 20 μg/cm2 of the FAB(x)-Pt/Ir
catalysts. The electrochemical active surface area (ECSA) of the Pt-based materials wasdetermined from the cyclic voltammetry (CV) curves in Figure 3-5, using an Ag/AgCl
reference electrode with 3 mol NaCl and a platinum counter electrode. The ECSA values were
calculated and presented in Table 3-3. In comparison with Pt-C [10] and Pt-TiOx [11] catalysts,
the FAB-based catalyst exhibits remarkably high ORR activity.
The ECSA of FAB60-Pt/Ir 2:1 was found to be higher than that of FAB180-Pt/Ir 1:1. A
comprehensive analysis of the electrochemical measurements can provide insights into theactivity and potential of the FAB(x)-Pt/Ir catalysts for use in Li-air batteries.

(Reference Electrode: Ag/AgCl Counter Electrode: Pt Scan speed: 50 mV/sec Gas: Nitrogen)
CV imagine with 0.1M perchloric acidFig 3-5 CV90

Table 3-3 ECSA from CV curve
SampleECSA/[m2/g]

FAB60-Pt/Ir 1:1

38.8

FAB60-Pt/Ir 2:1

134.1

FAB180-Pt/Ir 1:1

37.4

FAB180-Pt/Ir 2:1

41.6

Pt-FAB[Rrf.10]35

Pt-Vulcan XC-72 [Rrf.10]

31.5

Nb–Ti4O7 [Rrf.11]

45

The CV measurements in nonaqueous medium provided valuable information on theperformance of the FAB180-Pt/Ir 1:1 sample, which is a promising candidate for use in Li-air
batteries (Fig 3-7). The results showed that the oxidation peak occurred at 1.32 V, indicating
the decomposition of Li2O2, while the reduction peak was observed at -1.53 V, whichcorresponds to the formation of Li2O2. Interestingly, after 50 cycles, the OER peak was notclearly visible, but after 100 cycles, a change was observed around the 1.32 V and -1.53 V
peaks, and after 250 cycles, the OER peak appeared more clearly, also the peak area waschanged less during cycles going large. This suggests that the OER activity of the FAB180Pt/Ir 1:1 sample was improved during the cyclability studies, possibly due to the formation of
more active IrO2.
In the case of FAB180-Pt10% sample, on the other hand, lost its OER activity and even its
ORR activity quickly, with a lower current density than the FAB180-Pt/Ir 1:1 sample in the
OER peak. The results demonstrate the superior performance of the FAB180-Pt/Ir 1:1 sample
over the FAB180-Pt10% sample (Fig 3-6).
In summary, the electrochemical properties of the FAB(x)-Pt/Ir catalysts were examinedthrough CV testing under nonaqueous electrolyte, providing useful information on their abilityof catalysts to maintain high activity during OER. These properties are essential for assessing
their suitability for use in Li-air batteries. The research emphasizes the significance ofconsidering factors such as metal composition and cycling stability when selecting catalystmaterials for Li-air batteries.

91

(Reference Electrode: Ag/Ag+ Counter Electrode: Pt Scan speed: 50 mV/sec Gas: Oxygen)Fig 3-6 ORR results in 0.1M LiTFSI in TEGDME (a) with FAB180-Pt/Ir 1:1 (b) with FAB180-Pt10%

92

3.4.3. Charge-Discharge
In the series of the charge-discharge tests, the Li-air batteries were subjected to various
measurement conditions. A current value of 0.0192 mA was applied, and the cutoff voltage
was set at a potential (V) ≤ 2 V or ≥ 4.5 V. There was a pause time of 30 seconds between
charging and discharging, and the O2 pressure was set at 0.1 MPa. The charging anddischarging time were set at 8 hours, ensuring that the battery was fully charged and discharged.
Table 3-6 compares performance of FAB-based electrocatalysts and highlights differences in
overpotential between the 1st and 25th cycles (Fig-3-8). It is evident that both FAB180-Pt/Ir
1:1 and FAB180-Pt/Ir 2:1 exhibit overpotentials below 1V, with values of 0.38 V and 0.67 V,
respectively. Table 3-6 compares the performance of FAB-based electrocatalysts andhighlights the differences in overpotential between the first and 25th cycles. It is apparent that
FAB180-Pt/Ir 1:1 and FAB180-Pt/Ir 2:1 exhibit overpotentials below 1V, with respective
values of 0.38 V and 0.67 V. Figure 3-9 illustrates a gradual increase in overpotential from thefirst to the 25th cycle. All batteries were able to complete 25 cycles of charge-discharge at a
capacity of 1000 mAh/g, as shown in Figure 3-10.
The data in Table 3-5 reveals that FAB-60 based catalysts, such as FAB60-Pt/Ir 2:1, exhibit anoverpotential of up to 2.7V, which approaches the limit. Even FAB60-Pt/Ir 1:1 shows an
overpotential of 1.7V.
When different composition of Pt:Ir (1:1 and 2:1) were compared in the FAB-60 catalysts, it isclear that the overpotential was much lower for the 1:1. This suggests that Ir is participating in
the OER reaction and has an impact on the overpotential during charging. In contrast, FAB60Pt/Ir 2:1 demonstrates that if Ir loses its OER activity or cannot control the charging process,the overpotential will become unmanageable.

93

Table 3-6 The overpotential of batteries

Overpotential (V)FAB60-Pt/Ir 1:1

FAB60-Pt/Ir 2:1

FAB180-Pt/Ir 1:1

FAB180-Pt/Ir 2:1

1.72

2.71

0.38

0.67

1000

1000

1000

1000

100

100

100

100

Discharge
Capacity(mAh/g)Columbic Effect%94

Fig 3-8 Charge discharge behaviours of Li-air battery

95

440

420

660
640

400
620
380

600
580

360
560
340

Overpotential (mV vs Li/Li+)

Overpotential (mV vs Li/Li+)

680

540
FAB180-Pt/Ir 1:1
FAB180-Pt/Ir 2:1

520

320
0

5

10

15

20

25

Cycle

Fig 3-9 Overpotential of FAB-180 type catalysts-based LAB during 25 cycles.

Fig 3-10 Discharge capacity and columbic efficiency of with FAB-180 type catalyst-based LAB
during 25 cycles.

96

The Li-air battery with the FAB180-Pt/Ir 1:1 catalyst exhibited a discharge capacity of
approximately 3000 mAh/g, as shown in Figure 3-11. Figure 3-12 displays the effect ofdifferent current rate during charge-discharge, with a capacity set at 500 mAh/g. It wasobserved that at higher current rates, several issues arose during discharge, such as rapid
attainment of the voltage upper limit and a fast increase in overpotential. However, at or below
500 mA/g, the battery performed well during charge-discharge cycles. When the current
exceeded 500mA/g during discharge, damage occurred, and the voltage upper limit wasquickly reached. Therefore, it can be concluded that the Li-air battery in this study cannot
handle high current rates of above 500 mA/during charge-discharge cycles.

Discharge only

V (mV)

3000

2500

2000

0

1000

2000

3000

Ah/g(cycle) (mAh/g)

Electrolyte : 1.0 M LiTFSI with 0.1M LiI in TEGDME
Discharge current rate : 200mA/g.
Fig 3-11 FAB180-PT/Ir 1:1 with discharge only.

97

4500

V (mV)

4000

3500
cycle 1 50mA/g
cycle 6 100mA/g
cycle 11 200mA/g
cycle 16 500mA/g
cycle 21 1000mA/g
cycle 26 50mA/g

3000

2500

2000
0

50

100

150

200

250

300

Ah/g(cycle) (mAh/g)

Electrolyte: 1.0 M LiTFSI with 0.1M LiI in TEGDME
Target capacity: 500mAh/g catalyst
Fig 3-12 Chagre-discharge with FAB180-Pt/Ir 1:1 with change current rate

98

3.5.

Conclusion

The FAB(x)-Pt/Ir catalysts demonstrated exceptional activity in both ORR and OER, which is
attributed to the unique properties of the carbon support material and Pt/Ir nanoparticles
structure. These results offer a promising pathway for developing high-performance Li-air
batteries with FAB(x)-Pt/Ir catalysts. With such promising findings, further research is needed
to explore the full potential of these catalysts in Li-air battery technology. The insights gained
from this study will be valuable in the development of future catalyst materials and Li-air
battery systems.

99References[1] Vicente, J. R., Kordesch, M. E., & Chen, J. (2021). Stabilization of mixed-halide lead perovskites
under light by photothermal effects. Journal of Energy Chemistry, 63, 8-11
[2] Girishkumar, G., McCloskey, B., Luntz, A. C., Swanson, S., & Wilcke, W. (2010). Lithium− airbattery: promise and challenges. The Journal of Physical Chemistry Letters, 1(14), 2193-2203.
[3] Christensen, L., Fischer, N., Kroffke, S., Lemburg, J., & Ahlers, R. (2011). Cost-effective
autonomous robots for ballast water tank inspection. Journal of ship production and design, 27(3),127.
[4] NASA GISS Surface Temperature Analysis (v4), <https://data.giss.nasa.gov/gistemp/graphs_v4/>,(2019).
[5] Ghosh, S. K., & Rahaman, H. (2019). Noble metal–manganese oxide hybrid nanocatalysts. In Noble
Metal-Metal Oxide Hybrid Nanoparticles (pp. 313-340). Woodhead Publishing.
[6] Badam, R., Vedarajan, R., Okaya, K., Matsutani, K., & Matsumi, N. (2016). Sacrificial reducing agent
free photo-generation of platinum nano particle over carbon/TiO2 for highly efficient oxygen reduction
reaction. Scientific Reports, 6(1), 1-7.
[7] da Silva, G. C., Fernandes, M. R., & Ticianelli, E. A. (2018). Activity and stability of Pt/IrO2
bifunctional materials as catalysts for the oxygen evolution/reduction reactions. ACS Catalysis, 8(3),2081-2092.
[8] Zhang, Z., Zhang, Y., Fan, H., Wang, Y., Zhou, C., Ren, F., ... & Chu, J. (2017). A Janus oil barrel
with tapered microhole arrays for spontaneous high-flux spilled oil absorption and storage. Nanoscale,9(41), 15796-15803.
[9] Lettenmeier, P., Wang, L., Golla‐Schindler, U., Gazdzicki, P., Cañas, N. A., Handl, M., ... & Friedrich,
K. A. (2016). Nanosized IrOx–Ir catalyst with relevant activity for anodes of proton exchange membraneelectrolysis produced by a cost‐effective procedure. Angewandte Chemie International Edition, 55(2),742-746.
[10] Badam, R., Vedarajan, R., & Matsumi, N. (2015). Platinum decorated functionalized defective
acetylene black; a promising cathode material for the oxygen reduction reaction. Chemical
Communications, 51(48), 9841-9844.
[11] Ma, Y., Kajima, H., Shimasaki, Y., Nagai, T., Napporn, T. W., Wada, H., ... & Mitsushima, S. (2022).
Degradation Analysis of Pt/Nb–Ti4O7 as PEFC Cathode Catalysts with Controlled Arc Plasmadeposited Platinum Content. Electrochemistry, 90(5), 057004-057004.

100

4. Chapter 4
Total Conclusion
4.1.

Conclusion of This WorkAs we move into the new century, finding sustainable energy sources has become more urgent
due to the challenges posed by global warming. Green energy has become a key focus in the
21st century, and renewable energies are cleanest sources of energy. However, the challenge
lies now to store such energies.
One of the most promising technologies is the metal-air battery, which has been around since1868 when the basic model was first proposed by Leclanche. In ideal conditions, Li-air
batteries have been found to show very high energy density values, even comparable togasoline at 11680 Wh/Kg, and approximately 10 times higher than Li-ion batteries. This
represents a significant breakthrough in energy technology.
In chapter 1, it is crucial to have effective electrocatalysts to aid in the Oxygen Reduction
Reaction (ORR) and Oxygen Evolution Reaction (OER) in the Li-air battery. Carbon-basedmaterials are commonly used for this purpose due to their ability to maintain a large specificsurface area and conductivity. The ORR and OER are two types of metal-catalysed reactions,and their activity under Li-air battery conditions is key to the battery's performance.
To promote the widespread application of all types of metal-air batteries, the catalyst is an
important factor in their charge and discharge performance. For example, in Figure 4-1, therelationship between the electrolyte and oxygen on the surface of the Li-air battery cathodeusing catalysts is shown. Discussions revolving around the cathode materials and catalysts formetal-air batteries are hot topics in this area of research. With ongoing research anddevelopment, we are making strides towards more sustainable energy sources, and the Li-air
battery, which offers high energy density values. This could help us reduce our reliance on
fossil fuels in the years to come.

101

Fig. 4-1 Models of the reaction zones for catalytic reduction of oxygen: (a) a “three- phase reactionzone” for aqueous electrolyte metal/air battery and (b) a “two-phase reaction zone” for non-aqueous
electrolyte Li–air battery (the original figure is insignificantly modified)

Chapter 2 of this thesis focuses on synthesis of materials aimed at improving the performanceof Li-air batteries, with a particular emphasis on dual catalyst design. Figure 4-2 shows thedesign of the catalyst and the basic synthetic route. In this study two carbon based bifunctionalized catalysts, FAB-60 and FAB-180, were obtained by varying the oxidation
reaction time of AB carbon. These FABs have different oxygen contents and physical andchemical properties. Four types of electrochemical catalysts were designed, synthesized, andtested by controlling the weight percent of the metal loaded on the carbon. The microstructureof the FAB(x)-Pt/Ir family catalysts was influenced by the functional groups present in the
carbon and the weight percent of the metal. The ideal effective area was observed to be larger
when the weight or molar percent of Pt and Ir in the alloy was close to one another. If the
carbon standard can support sufficient functional groups for metal bonding, the size of thenanoparticles can be uniformly controlled to be in the nanoscale range.
This research provides valuable insights into the development of high-performance Li-air
batteries using FAB(x)-Pt/Ir catalysts. The FAB(x)-Pt/Ir catalysts demonstrated exceptional
activity in both ORR and OER, which is attributed to the unique properties of the carbon
support material and Pt/Ir nanoparticles structure. These results offer a promising pathway fordeveloping high-performance Li-air batteries with FAB(x)-Pt/Ir catalysts. This is due to theunique properties of the carbon support material and the structure of the Pt/Ir nanoparticles.
102Effective electrocatalysts are crucial for the charge and discharge performance of all types ofmetal-air batteries, including Li-air batteries. Carbon-based materials are commonly used dueto their ability to maintain a large specific surface area and conductivity, making them thestandard materials for this purpose. The ORR and OER are two types of metal-catalyzed
reactions, and their activity under Li-air battery conditions is key to the battery's performance.
TEM analysis of the electrocatalyst revealed that FAB-180-based catalysts had a fully formed
lattice structure. However, obtaining accurate crystal phase information for FAB-60-based
catalysts was difficult.

Fig. 4-2 design and basic synthetic route103

Fig4-3 TEM with catalyst.

In Chapter 3 of this thesis, the results of electrochemical measurements were discussed. The
performance of cathode materials for Li-air batteries was evaluated. Among the various
cathode materials studied, the FAB(x)-Pt/Ir catalyst family has exhibited better ORR (oxygen
reduction reaction) and OER (oxygen evolution reaction) activity, surpassing that of othercatalysts previously reported in the literature. The electrochemical characterization has enabled
the determination of overpotentials and charge-transfer resistances, providing insight into theelectrochemical behavior of the Li-air batteries. Moreover, the results of charge-discharge tests
have shown the low over potential, and high discharge capacities and stable cycling of theFAB(x)-Pt/Ir catalysts as shown in Figure 4-4.
For example, the FAB180-Pt/Ir 1:1 catalyst based cell exhibited a discharge capacity of
approximately 3000 mAh/g, overpotential with values of 0.38V after 25 cycles. Total chargedischarge cycles up to 200 cycles were performed.

104

Fig 4-4. discharge capacity and columbic effect with FAB-180 carbon based catalyst during 25 cycles

105

4.2.

Future Scope of This Work

This work has promising implications for future research and materials design in the field of
Li-air batteries. The high-performance activity demonstrated in this study for ORR and OER
suggests potential for the development of related materials and new designs.
There are some possible outgrowths and ideas that can be explored based on the findings ofthis study, including:(a) Pt alloy based high performance OER catalyst, such as Pt/Ni, Pt/Fe, Pt/Fe/Ir.
(b) FAB(x)-Pt/Ir catalyst family-based cathode in PEMFC.

106