bluuebunny/crossref_metadata_2025 huggingface dataset:
Power Generation Characteristics of PEFCs Using Heteropolyacids As Anode Redox Mediators
Authors: Naruse Shinji , Muroyama Hiroki , Matsui Toshiaki , Eguchi Koichi
Published: December 2020

Polymer electrolyte fuel cells (PEFCs) have attracted much attention as clean power generation systems. PEFCs have been employed for residential cogeneration systems, fuel cell vehicles and spaceships due to short startup/shutdown times, small size, and low weight, compared to high– temperature FCs. Because precious metals such as Pt are utilized for electrocatalysts in order to obtain high power generation efficiency, high cost of the system is one of the issues in the spread period. In addition, hydrogen fuel has problems in safety and transportation.

Therefore, in recent years, PEFC using heteropolyacid (HPA) as a mediator has been reported for the solution of these problems [1]. In this system, reduced HPA is supplied to the anode, and is converted to oxidized HPA over the electrode via the following reaction.

[H
nXM
V

nM
VI
12–n
O40]
z

– → [XM
VI
12O40]
z

– + ne– + nH+

(1)

where X = Si, P and M = W, Mo, V

On the other hand, oxygen is reduced to produce water on the cathode, as in the case of general PEFCs. This PEFC system can be continuously operated by reducing the oxidized HPA and supplying it to the anode again. Electrochemical methods and addition of reducing agents can be considered for reducing oxidized HPA [2]. However, more effective reduction methods have been needed to achieve high performance and long-term operation.

In this study, various metal pieces were utilized for the reduction of oxidized HPA in order to establish an effective method. The effect of metal pieces on the power generation performance and long-term operation of PEFC was evaluated. H3PW12O40·28H2O (PW12) and H2SO4 were added to ultrapure water to prepare an oxidized PW12 solution (0.01 M PW12–0.5 M H2SO4). This solution was subjected to a constant current electrolysis (1.00 mA cm–2) or an addition of metal pieces (Al, Ni, Fe, Co) to obtain the reduced PW12. A membrane–electrode assembly was prepared using Nafion® membrane as an electrolyte, carbon black as an anode, and Pt/C as a cathode. The operating temperature was 80 ºC, and O2 (relative humidity: 100%) was supplied to the cathode. The reduced PW12 solution bubbled with Ar gas was supplied to the anode by a liquid feed pump. Current–voltage (I–V) measurements and galvanostatic operation tests (5.00 mA cm–2) were performed using this single cell. As a result, the addition of Co pieces achieved the high reduction degree of HPA and the superior cell characteristics. The suppression of the side reactions such as hydrogen generation and the increase of the output power were necessary for the improvement of PEFC system using HPA as the anode redox mediator.

[1] R. Singh, A. A. Shah, A. Potter, B. Clarkson, A. Creeth, C. Downs, F. C. Walsh, J. Power Sources, 201 (2012) 159–163.

[2] S. Nakada, E. Morikawa, T. Okanishi, H. Muroyama, T. Matsui, Y. Hirao, K. Eguchi, Abstract of 82th Meeting of Electrochem. Soc. Jpn., 3B09 (2015).
Development of Electrochemically-Driven CO2 Separator for Hydroxide Exchange Membrane Fuel Cells in Transportation Applications
Authors: Matz Stephanie , Setzler Brian , Weiss Catherine M. , Shi Lin , Gottesfeld Shimshon , Yan Yushan
Published: December 2020

Hydrogen fuel cell vehicles are a promising, emerging alternative to the internal combustion engine but the commercialized proton exchange membrane fuel cells (PEMFCs) are comparatively expensive. Hydroxide exchange membrane fuel cells (HEMFCs) are a potentially lower cost hydrogen fuel cell technology under development; unfortunately, ambient levels of CO2 in air reduce HEMFC performance and impede HEMFCs from becoming competitive with the incumbent fuel cell technology.1 Current levels of atmospheric CO2 have been shown to decrease fuel cell performance up to 200 mV.2 The hydroxide produced during the electrochemical reaction in a HEMFC reacts readily with CO2 in air at the cathode due to its acid-base reaction and transports CO2 across the hydroxide exchange membrane. At the anode, the bicarbonates build up lowering the local pH until CO2 evolution is favorable, concurrently the pH gradient saps cell voltage. However, this transport results in the effective separation of CO2 from air. By optimizing a HEMFC for CO2 capture, rather than power production, an electrochemically-driven CO2 separator (EDCS) was developed using a poly(aryl piperidinium) membrane.3 The continuous and compact EDCS has the potential to enable HEMFCs to operate efficiently with ambient air in automotive applications.

This work will demonstrate the ability of the EDCS to effectively and continuously remove CO2 from air at ambient levels using minimal hydrogen flow to power the separation. This work will explore the effect of operating conditions such as flow rates, current density, and relative humidity on CO2 separation performance with the innovative EDCS. A carbon-ionomer interlayer between the catalyst layer and membrane was added to improve CO2 capture by creating an accessible volume for hydroxide and CO2 gas to react. Additionally, various design features of the cell were investigated to improve the mass transport such as flow fields and gas diffusion layers. The CO2 removal performance of a single-cell 25 cm2
EDCS is shown in Figure 1. Currently, the optimal design configuration of the EDCS has achieved 98% CO2 removal for 100 hours (Figure 2) with the potential to improve CO2 removal as well as processed gas throughput by further development of the module’s design.

References:

B.P. Setzler et al., Nature Nanotechnology 11, 12, 1020-1025 (2016).

N. Ziv et al., Chemsuschem, 11, 7, 1136-1150 (2018).

J. Wang et al., Nature Energy, 4, 5, 392-398 (2019).

Figure 1
Development of High-Efficient Ion Selective Membrane Separator for Lithium Polysulfide Redox Flow Batteries
Authors: Fifield Natalie , Wang Xiaofeng , Wang Tongshuai , Kim Sangil , Bae Chulsung
Published: December 2020

As our society demands greater utilization of intermittent renewable energies from solar and wind, the development of a low cost, reliable energy storage technology with high energy density is of great interest. In particular, highly efficient large-scale electrochemical energy storage has been an important issue to enhance the efficiency and quality of electrical grid. Among many energy storage systems, lithium-polysulfide (Li-PS) redox flow batteries (RFBs) have been considered one of the most promising electrochemical storage systems because they can offer the high energy density of the Li-S batteries and the general features of RFBs (e.g. flexible system design from decoupled energy storage, a power generation, safer operation, long cycle life) simultaneously. To successfully adopt Li-PS RFBs for a large scale electrochemical storage technology, it is imperative that the membrane separator should prevent the crossover of redox-active materials between the electrodes which would otherwise result in low columbic efficiency, rapid capacity fading and poor cycle life. Recently, Bae group demonstrated that aromatic polymers based on biphenyl backbones have excellent chemical and mechanical stability and prevent crossover of redox-active materials for RFBs. In this work, we will present new, multifunctional, highly ion selective, biphenyl polymer (BPSA) with high ionic transport properties (Figure 1). The unique design of this polymer involves (1) a lithiated sulfonate group, (2) tunable hydrophobic polymer backbone, and (3) a hydrocarbon linker between them. The covalent connection of these two distinctively different moieties would lead to nanometer-scale phase separation between hydrophilic ion conducting channels (via aggregation of sulfonated groups) and hydrophobic polymer backbone domains. The BPSA membranes demonstrated resistance in swelling in the commonly used Li-S RFB solvent solution dioxolane/dimethoxyethane (15% in x-y direction) and achieved good mechanical properties (tensile strength ≥20 MPa, percentage elongation ≥50). In an effort to decrease the areal resistance and increase lithium conductivity of the polymer membranes, a variety of reinforcement materials such as poly(ethylene) (PE), polytetrafluoroethylene (PTFE), and Celgard were coated with a thin layer of BPSA. The low-cost, chemically inert, reinforcing materials provide additional mechanical strength and reduce the swelling ratio of BPSA, lowering the permeation rate of the polysulfide anions. Performance of these hydrocarbon cation exchange membranes in Li-S RFB with respect to the separation of polysulfides and conductivity are compared to the state-of-the-art cation exchange membrane Nafion®, and will be discussed. A brief description of battery performance carried out by UIC will follow.

Figure 1
Molecular Dynamics Study of Ionomer Aggregate Structure during Solvent Evaporation
Authors: Mabuchi Takuya , Tokumasu Takashi
Published: December 2020

Cathode catalyst layer (CL) is one of the principal components for polymer electrolyte fuel cells. CL is typically prepared by solution processing techniques where a catalyst ink consisting of Pt-C (platinum on a carbon powder support), ionomer, and solvents (water/alcohol mixtures) is exposed to evaporation. The structure and stability of ionomer aggregates in solutions are the key to the physical properties of ionomer thin films. Thus, understanding the ionomer aggregation behaviors in solutions is of great importance to gain a deep insight into fundamental morphological characteristics of ionomers. In our previous studies, we have observed ionomer formation into cylindrical bundle-like aggregates in solutions. The size of ionomer bundles decreases with increasing alcohol content, indicating that the ionomers tend to be more dispersed at higher alcohol content, which is in good agreement with the trend inferred from the scattering experiments. In this study, evolution of ionomer aggregate structure in water solutions have been investigated using solvent evaporation simulations based on the course-grained molecular dynamics method, as shown in FIgure 1. The balance between evaporation, sedimentation, and diffusion was controlled by the dimensionless Peclet number, providing a link between experiments and simulations. The effects of substrate wettability on the ionomer thin film structure will be discussed in the presentation.

Figure 1
Impact of Microstructured Morphology on Macroscale Properties of Semi-Crystalline Triblock Copolymer Anion Exchange Membranes
Authors: Trant Carrie , Bae Chulsung , Lee Sangwoo
Published: December 2020

The ability of polymer-based ion exchange membranes to efficiently transport ions is important in a wide range of electrochemical energy applications including fuel cells, batteries, and electrolyzers. To better understand the impacts of microstructured morphology on water uptake and the formation of hydrated ion conducting channels to aid ion conductivity, we investigated the effects of polydispersity and ion exchange capacity (IEC) on the microscopic and macroscopic structures and the performance of the semi-crystalline poly(ethylene-b-quaternized styrene-b-ethylene) (ESE) triblock copolymer-based anion exchange membranes (AEMs). The quaternary ammonium group functionalization of the styrene middle block was quantitatively controlled by acid-catalyzed Friedel-Crafts bromoalkylation reaction followed by amination with trimethylamine to synthesize membrane materials with a range of IECs of 0.64 to 1.89 meq/g. Our results suggest that strongly-segregated microdomains without a long-range order are desirable for membrane processing and performance compared to the other membranes with anisotropic lamellar morphology.
Influence of Surface Potential at Aqueous/TiO2 Thin-Film Interface on the Capacitance Performance
Authors: Wang Yang , Gao Tian , Tan Wei , Anderson Marc A.
Published: December 2020

Electrochemical capacitors and capacitive deionization store energy through the interfacial layer formed between electrodes and electrolytes. TiO2 thin-film deposited on Si wafers was studied by ellipsometry under controlled humidity to explore the refractive index (dielectric constant) of pore water. The surface potential measured by electrophoretic mobility at different equilibrated pH and specific adsorbing ion concentrations influences the refractive index of pore water. The higher the surface potential, the higher the refractive index, the lowest refractive index occurring close to the isoelectric pH. The presence of the specific adsorbing ions on the nanopore walls increases the refractive index. Furthermore, galvanostatic charge/discharge measurements were performed using TiO2 thin films coated on platinized Ti coupons to obtain the capacitance of the aqueous TiO2 thin-film systems. The capacitance followed a similar trend as the surface potential and can be improved by specific adsorbing ion addition over the pH range of 5 to 9. In addition, the crystalline structure of TiO2 thin-film varied by different sintering temperatures also influences the surface potential, resulting a different capacitive performance. At elevated sintering temperature, TiO2 transfers from anatase to rutile with an increased surface potential. The electrochemical tests show that the electrode capacitance increases from 19.50 to 41.82 mF/cm2. The investigation of oxide materials in the application for electrochemical capacitors and capacitive deionization could be another possibility other than carbon materials.
Interstitial Bimetallic Doping into Carbon Nanofibers By Electrospinning Technique: Electrochemical Supercapacitors
Authors: Son You-Hyun , Akhtar M. Shaheer , Yang O-Bong
Published: December 2020

Last decade, the supercapacitors (SCs) are well-recognized as promising energy storage devices because of their high-power density, long cyclic life, fast charge and discharge rates, and facile operational mechanism. Carbon materials such as active carbon, carbon nanotubes (CNTs), mesoporous carbon, graphene, etc. are highly suited electrode materials for supercapacitors owing to their high specific surface area, high electronic conductivity, and chemical stability against the corrosive electrolytes. In recent years, the mono or bimetallic transition metal doping into carbon materials has received immense attention because they significantly enhance the mechanical strength, electrochemical and physicochemical properties. Therefore, it is expected that the bimetallic doping into carbon nanofibers (CNFs) can be an innovative electrode for supercapacitors as they might improve the electrocatalytic and corrosive properties. In this work, the nickel (Ni) - copper (Cu) doping into the CNFs were prepared by a facile and controlled cost-effective electrospinning technique followed by stabilization of electrospun nanofibers. The prepared Ni-Cu doped CNFs were carbonized in the furnace for the partial decomposition of the polymer and irregular decomposition of the metallic acetate to complete NiCu in CNFs. By analyzing morphological characterizations, the NiCu was interstitially doped into CNFs. The surface analysis results revealed that NiCu doped CNFs exhibited a highly porous structure with a specific surface area of 244 m2/g and a large pore volume. The prepared NiCu doped CNFs were applied as the electrode and demonstrated exemplary electrochemical property with a reasonable specific capacitance of 337.5 F/g at 10 mV/s in aqueous 1M Na2SO4 electrolyte.
(Invited) Digital Twin-Driven Battery Modeling: Understanding the Physical and Electrochemical Behavior during Fast-Charging
Authors: Lee Yong Min , Park Joonam
Published: December 2020

Long charging time is one of major inconveniences in choosing electric vehicles (EVs). In order to solve it, shortening the charging time within fifteen minutes or less is set to satisfy EV customers. However, without deep understanding both electronic and ionic behaviors within the battery, to analyze and predict the physical and electrochemical behaviors must be limited. Furthermore, the unbalance between electron and ion flows becomes more harsh as the charging rate increases. Thus, building a virtual 3D structural and electrochemical model and simulating it must be a powerful tool to look into the inside the battery during fast charging. In this work, a new digital twin battery technology, combining 3D structural and electrochemical modeling tools, is introduced and some case studies are shown to suggest how to improve the fast charging characteristics as a point of material properties and cell designs as well. Especially, electronic and ionic current flows, surface overpotential, local state-of-charge, etc are estimated and compared systematically.
In-Situ High-Temperature X-Ray Absorption Spectroscopy of Fe-N-C Electrocatalysts during Pyrolysis
Authors: Mufundirwa Albert , Yoshioka Satoru , Sugiyama Takeharu , Harrington George Frederick , Hayashi Akari , Sasaki Kazunari , Lyth Stephen Matthew
Published: December 2020

Deeper understanding of the formation of active sites during the pyrolysis of iron-nitrogen-carbon (Fe-N-C) electrocatalysts for the oxygen reduction reaction (ORR) is required. Here, we present a nitrogen-doped carbon foam support treated at high temperature (1600 °C) to stabilise the material properties. Iron-containing precursors are then adsorbed onto the surface, followed by heat treatment. This changes the chemical state of the adsorbed iron, whilst the material properties of the support are effectively unchanged. The two-step synthesis method used to create these model electrocatalysts decouples porosity, microstructure, and conductivity from the electrochemistry, which can instead be attributed mainly to changes in the chemical environment of iron.

Advanced characterisation techniques such as in-situ high-temperature X-ray absorption spectroscopy (HT-XAS) and high-temperature near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) are employed to gain insights into the state of the adsorbed iron as it decomposes during pyrolysis to form active sites. Transmission electron microscopy (TEM) is used to track the microstructure for different types of precursor heated at different temperatures. Meanwhile, in-situ electrochemical XAS is used to understand how the chemical environment of the catalysts change during the ORR.

The results are discussed by relating different chemical environment with the electrochemical ORR activity. Despite the two-step synthesis technique, these model Fe-N-C electrocatalysts are highly active. The load-cycling durability and start-stop durability are measured, and the degradation mechanisms are discussed.
Intermetallic Co-Pt/C Nanoparticles Synthesized Via Sonochemical Method As Enhanced Electrocatalysts for Cathode of PEMFC
Authors: Kwon Young-Uk , Park Ah-Hyeon
Published: December 2020

For fuel cell stack of 80 kW, platinum for electrocatalyst requires around 10 g per fuel cell electric vehicle (FCEV). A large-scale synthesis method for the low-platinum catalyst is necessary for this field to reduce man-power. Ultrasound-assisted polyol synthesis (UPS) is a method for the preparation of small and uniform size transition metal core-platinum shell nanoparticles evenly distributed on the support. Platinum(Ⅱ) acetylacetonate, Cobalt(Ⅱ) acetylacetonate, and carbon support were dispersed in ethylene glycol which is reducing agent and irradiated by ultrasound for 3 h to reduce the precursor to metal nanoparticles, followed by washing and drying to obtain a powder. The characterization was observed by solution color visualization, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and electrocatalytic performance. Also, the synthesized samples were calcined at various temperatures to cause the atomic rearrangement to the most stable arrangement, and atomic accumulation of boundary between each atom and compression of platinum lattice that affects activity or durability of electrocatalyst has changed. Synthesized sample with optimized synthesis and treatment condition shows improved electrochemically active surface area (ECSA) and Oxygen reduction reaction (ORR) catalytic activity in the half-cell test and durable catalytic activity in the performance evaluation of membrane-electrode assembly (MEA) compared to existing Platinum catalyst. As renewable energy conversion and storage system is one of the main challenges, FCEV is developed to solve pollution from CO2 emission and oil depletion issues. Our low-platinum nanoparticle with uniform distribution synthesized using a sonochemical method will replace precious metal catalysts used in fuel cells instead of platinum catalysts.
(Invited) Towards Solving the Long Standing Mystery of the Chemical State of Co in PtxCo1-X to Boost HOR and ORR
Authors: Oezaslan Mehtap , Weber Philipp , Weber Daniel Jochen , Dosche Carsten
Published: December 2020

Recently, Pt-based core-shell nanoparticles (NPs) have emerged as highly active catalyst materials to accelerate the sluggish oxygen reduction reaction (ORR) in acidic media as well as the hydrogen oxidation reaction (HOR) in alkaline. Less attention has been payed to the chemical state of the less noble metal after forming core-shell NPs. Intuitively; a metallic state of the less noble metal inside the particles has been suggested from many research groups.

In this talk, we will show a new catalyst concept for Pt-Co nanoparticles by manipulating the surface arrangement and composition induced by the reaction conditions. More precisely, our catalysts exhibit superior Pt surface area-based specific activities (up to 10-fold) and Pt mass-based activities (up to 5-fold) towards the ORR compared to commercial Pt/C at 0.95 VRHE. In addition, we will show the influence of the chemical state and surface enrichment of the cobalt on the HOR activity in alkaline media.

Altogether, we will solve the long standing mystery of the chemical state of the cobalt and its distribution for PtxCo1-x nanoparticles and its remarkable effect on the catalytic performance for HOR and ORR.
(Keynote) 10-Minute Fast Charging of High Energy Density Lithium-Ion Batteries with Superior Cycle Life
Authors: Yang Xiao-Guang , Liu Teng , Ge Shanhai , Wang Chao-Yang
Published: December 2020

Adding 200 miles of driving range in 10 min by charging at 400 kW, the so-called extreme fast charging (XFC), is considered as the key to mainstream adoption of electric vehicles (EVs). No EVs today, however, can withstand 400-kW charging power due to the risk of Li plating, which severely deteriorates battery life.

Recently, our group reported an asymmetric temperature modulation (ATM) method that enables 10 min charging of high-energy EV cells with remarkable cycle life. [1] The key concept of the ATM method is to charge a Li-ion cell at an elevated temperature of 60oC and discharge (and stores) the cell at the cool ambient temperature (Figure 1). The high charging temperature effectively eliminates Li plating thanks to the enhanced kinetics and transport, and the limited time of exposure to 60oC (~10 min per cycle, or 0.1% of the lifetime of an EV) prevents severe SEI growth. We demonstrated that a high-energy cell with a specific energy of 209 Wh/kg sustained 2500 cycles of 10-minute XFC with only 8.3% capacity loss, far exceeding the US DOE target.

In this talk, we will give a comprehensive discussion of the ATM method. Also, we will share our latest progress on the XFC of cells with much higher specific energy (260 Wh/kg).

References

[1] X.G. Yang, T. Liu, Y. Gao, S. Ge, Y. Leng, D. Wang, C.Y. Wang, Joule, 3 (2019) 3002-3019.

Figure 1
Mesoscale Electrode Analytics for Fast Charging
Authors: Vishnugopi Bairav Sabarish , Chatterjee Debanjali , Verma Ankit , Mukherjee Partha P.
Published: December 2020

Fast charging of lithium-ion batteries is paramount toward widespread adoption of electric vehicles. Fast charging, however, poses safety concerns due to the occurrence of lithium plating and local thermal excursions. Preserving the thermal safety, performance and life of LIBs at such operating extremes necessitates a thorough understating of the thermal and degradation interactions emanating at the electrode level. In this work, the electrode-level implications of thermal and electrochemical characteristics of Li-ion cells during fast charge conditions is examined. Suggestions for improvement in fast charging capabilities via electrode engineering are made.
Sn–Ni Alloy Anode Pre-Doped in Vinylene Carbonate Containing Electrolyte for Lithium-Ion Capacitor
Authors: Nara Hiroki , Nakamura Yusuke , Ahn Seongki , Momma Toshiyuki , Sugimoto Wataru , Osaka Tetsuya
Published: December 2020

Lithium–ion capacitor (LIC), which is composed of non–Faraday reaction cathode used in electric double layer capacitor (EDLC), and Faraday reaction anode used in lithium–ion battery (LIB), is a promising energy storage device for electric vehicles, because LICs are ranked between LIBs and EDLCs for energy density and power density.1 LIC with Sn–Ni alloy anode is superior to that with a graphite anode in energy and power density. 2 For the purpose to improve its cycle durability to a practical level, the effect of vinylene carbonate (VC) which affects positively for LIBs, was investigated.

Sn–Ni alloy anode was electrodeposited according to the previous report.3 The Sn–Ni alloy anode was pre-doped (pre-lithiated) by several charge–discharge cycles in an electrolyte with or without vinylene carbonate (VC). The LICs composed of an activated carbon cathode and the pre-doped Sn–Ni alloy anode were evaluated.

The VC additive was revealed to affect positively during a pre-doping process and to affect negatively during charge–discharge cycling to the cycle performance of LIC. The difference for the additive effect was discussed by the potential changes and the morphology changes of the anode, revealing that VC formed a polymer-like SEI during the pre-doping process, suppressing deactivation of Sn caused by cracking growth and peeling-off during charge–discharge cycling. In contrast, VC was decomposed continuously during charge–discharge cycling with consuming pre-doped lithium. Thus, a strategy to use additives for alloying anode system was established. Finally, the excellent cycle durability (more than 10000 cycles with the capacity retention of 72.3%) of the LIC with high volumetric energy density of 38.9 Wh/L at 120 W/L was firstly demonstrated (Fig. 1).

Acknowledgement

This work is partially supported by Advanced Low Carbon Technology Research and Development Program of the Japan Science and Technology Agency (JST-ALCA, JPMJAL1008).

References

K. Naoi, S. Ishimoto, J. I. Miyamoto, and W. Naoi, Energy Environ. Sci., 5, 9363–9373 (2012).

S. Ahn, Y. Nakamura, H. Nara, T. Momma, W. Sugimoto, and T. Osaka, J. Electrochem. Soc., 166, A3615–A3619 (2019).

H. Mukaibo, T. Sumi, T. Yokoshima, T. Momma, and T. Osaka, Electrochem. Solid-State Lett., 6, A218 (2003).

Figure 1
Reaction Mechanism Exploration of Binary Oxide Bi2Mo3O12@Ti3C2 Composite As Anode for Li-Ion Capacitor
Authors: Tian Kai , Zhao Jianqing , Gao Lijun
Published: December 2020

Metal oxides as pseudocapacitive materials are widely explored as anode for lithium ion capacitors, owing to their high volumetric and gravimetric lithium storage capacities. We present studies on reaction mechanism of binary Bi2Mo3O12 oxide as an anode for lithium storage. In-situ synchrotron XRD measurements are performed on this exotic material to elucidate lithium storage behaviors, coupled with voltage resolved CVs and ex-situ XPS analyses. Synergistic effect is believed to be the factor on improving electrochemical performance of the binary metal oxide anode instead of simple combination of two single components. The Bi2Mo3O12 anode undergoes an initial irreversible conversion reaction resulting in metallic Bi and Li2MoO4 on electrochemical discharge down to 0.01 V vs. Li+/Li. During successive cycling, the two components reversibly uptake and release lithium ions through alloying/de-alloying and intercalation/de-intercalation reactions by forming Li3Bi alloy and Li2+xMoO4. Cycling stability of the Bi2Mo3O12 anode is considerably enhanced by in-situ composition of Ti3C2 MXene. The Bi2Mo3O12@Ti3C2 composite anode exhibits 227 mAh/g capacity upon prolonged 1000 cycles at 2.5 A/g high charge/discharge rate in the voltage range of 3.0 - 0.01 V. This performance indicates the Bi2Mo3O12@Ti3C2 composite can be a potential candidate as anode for Li-ion capacitors.
(Invited) A Transversal Low-Cost Pre-Lithiation Strategy Enabling Ultrafast and Stable Lithium Ion Capacitors
Authors: Arnaiz Maria , Shanmukaraj Devaraj , Carriazo Daniel , Bhattacharjya Dhrubajyoti , Villaverde Aitor , Armand Michel , Ajuria Jon
Published: December 2020

Lithium ion capacitors (LICs) are foreseen to be a complementary alternative of vital importance to current energy storage issues, coupling high energy density delivered by batteries with high power/long cycle life offered by supercapacitors. The prime issues in realising this technology are pre-lithiation and replacement of graphite electrodes that bring about energy gain at the expense of power. Herein we present an easy-to-scale-up approach, combining activated carbon with a highly efficient and industrially compatible low-cost sacrificial salt (dilithium squarate), that can be used as a lithium source for pre-lithiation. Paired with a hard carbon electrode tailored to perform at high rates, a LIC is demonstrated. Furthermore, the successful fabrication of a LIC pouch cell prototype with high energy at high power densities showing capacitance retention over 84% after 48000 cycles validates the strategy. This breakthrough may trigger the easy and low-cost fabrication of LICs and significantly reduce technological barriers to market growth and consolidation.

Figure 1. Scheme representing the pre-metallation strategy followed in this work: Open circuit) MICs are represented by pristine HC as the negative electrode, each electrolyte corresponding to LIC, NIC and KIC with cations represented in dark blue (Li+), dark red (Na+) and dark green (K+) while anions are represented in brown (ClO4
-) and grey (PF6
-), and AC combined with the sacrificial salt -whose ions are represented in light colors- as the positive electrode; 1st charge) Cations from electrolyte and sacrificial salt are inserted into the HC while PF6
- anions are adsorbed into the AC surface; 1st discharge) While the excess of cations coming from the sacrificial salt are permanently inserted into the HC to compensate for the first cycle irreversibility (light colored cations), cations from electrolyte are reversibly inserted/deinserted as well as anions are adsorbed/deadsorbed allowing MICs to operate efficiently.

Figure 1
Expanding Interlayer Spacing in MoS2 for Realizing an Advanced Supercapacitor
Authors: Sarkar Debasish , Das Debanjan , Das Sarma Dipankar , Shukla Ashok Kumar
Published: December 2020

Charge-storage mechanism of free-standing MoS2/r-GO (r-GO = reduced graphene oxide) hybrid nanoflakes on molybdenum (Mo) foil in Na2SO4 solution is elucidated for realizing a high-performance asymmetric supercapacitor (ASC). Thiourea that acts primarily as sulfur source also helps intercalating ammonium ions, which along with r-GO facilitate in-situ exfoliation of MoS2, producing hierarchical MoS2 with expanded interlayer spacing. This interlayer expansion in MoS2 facilitates Na+-ions intercalation/de-intercalation, and ensures enhanced capacitance, rate capability and cycling stability of the capacitor. Besides exhibiting attractive energy-cum-power traits, the 2V MoS2/r-GO//Fe2O3/MnO2 ASC shows compelling cycling performance for over 20,000 cycles in an aqueous electrolyte.

Figure 1
Investigation of Pd-Containing Co3O4/C Catalysts for Oxygen Reduction Reaction
Authors: Stagniunaite Raminta , Kepeniene Virginija , Vaiciuniene Jurate , Tamasauskaite-Tamasiunaite Loreta , Norkus Eugenijus
Published: December 2020

Because of the energy crisis, air pollution and global warming it is necessity of technologies that creates sustainably, highly efficient and green energy resources. That is the reason why fuel cells are one of the best power sources – they convert chemical energy into electrical energy and do not contaminate the environment. The main difference between fuel cells and usual batteries is that fuel cell requires a continuous source of fuel (ethanol, methanol, ethylene glycol etc.) and oxygen to sustain the chemical reaction. It is well known that Pt-based catalysts are usually used in fuel cells, however recently, the search of new catalysts with reduced amount of Pt or even non-noble metal catalysts is in progress. Pd-based electrocatalysts have been studied as alternative because of their lower cost and efficient electrocatalytic activities for oxygen reduction (ORR) and fuel oxidation (ethanol, methanol, ethylene glycol etc.) reactions.

In this paper we investigated electrocatalytic activity of the Co3O4/C based Pd catalysts towards oxygen reduction reaction. The new catalysts were prepared using few different synthesis steps. At first Co3O4 was deposited on carbon using microwave irradiation at 120 ºC for 3h. Then the obtained Co3O4/C powder was impregnated by Pd in 0,0014 M PdCl2 solution. Further, part of the Co3O4/C powder and impregnated Co3O4/C powder was annealed at 400 ºC for 3h. Depending on the fabrication conditions four different composition of catalyst was obtained. The composition, morphology and structure of the prepared catalysts were characterized using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Electrochemical measurements have been carried out using linear sweep voltammetry (LSV) using rotating disk electrode (RDE) method.

The XRD and XPS data have been showed that the constitution of obtained catalysts was following: Co3O4/C was obtained after microwave irradiation heating, PdCox(OH)y/C constitution was estimated for catalyst impregnated in 0,0014 M PdCl2 solution and Co3O4/C-T and PdOCo3O4/C catalysts were obtained annealed at 400 ºC for 3h.

It has been found that the impregnation of the Co3O4/C substrate by Pd as well as annealing of primary materials strongly enhanced electrocatalytic activity of investigated catalysts towards oxygen reduction reaction. The ORR activity of the catalysts has been found to increase as follows Co3O4/C < Co3O4/C-T < PdCox(OH)y/C < PdOCo3O4/C ≤ Pt/C. The ORR onset potential reached the most positive potential values in the same line and was equal to 0.78 < 0.83 < 0.91 < 0.92 < 0.95 V.

It has been determined that the PdOCo3O4/C catalyst showed the highest electrocatalytic activity for ORR compare to the PdCox(OH)y/C and Co3O4/C catalysts and was very similar to Pt/C.
Investigation on Preparation Conditions for High Performance MEA of Alkaline Membrane Fuel Cells
Authors: Lee Hyejin , Shin Dongwon , Bae Byungchan
Published: December 2020

Recently, AMFCs (Alkaline Membrane Fuel Cell) using non-platinum group metal (PGM) based catalysts and having good efficiency have attracted attention as an alternative to PEMFCs. However, in spite of these important advantages, the development of materials for AMFC is still an important issue because the AMFC performance based on the platinum catalyst is still superior to that of non-PGM in an alkaline environment. [1]

We here present various preparation methods of a membrane electrode assembly (MEA) in order to increase the performance of AMFCs. Kinds of the gas diffusion layer, solvents for catalyst slurry, commercial binders for electrodes, and PGM-free catalyst were the main parameters of MEA performance. For the exact comparison of each parameter, reference MEA was selected by the use of commercial parts such as 39BC (SIGRACET), Fumion membranes, and binders (FuMA-Tech Inc.,), Pt/C and PtRu/C (Tanaka Kikinzoku Kogyo K.K.). The cell test was performed at 70 °C and 100% RH with 1 L/min H2/O2 to both anode/cathode, respectively.

As a result, the FAA-3-50 membrane with PGM catalyst layers showed excellent performance of over 1,000 mA/cm2 at 0.6 V. In addition, the performance of the PGM-free cathode catalyst was over 450 mA/cm2, which showed a possibility to non-PGM AMFCs. We observed the I-V curve, electrochemical surface area, linear sweep voltammograms, and ohmic resistance. Experimental conditions and results will be presented in detail.

References

[1] H. A. Firouzjaie, W. E. Mustain, ACS Catal., 10 (2020) 225-234
(Invited) Development of Versatile Polymer Materials for Anion Exchange Membranes in Electrochemical Energy Conversion Technology
Authors: Bae Chulsung
Published: December 2020

Anion exchange membranes (AEMs) based on hydroxide-conducting polymers are a key component for anion-based electrochemical energy technology such as fuel cells, electrolyzers, and advanced batteries. Although these alkaline electrochemical applications offer a promising alternative to acidic proton exchange membrane electrochemical devices, access to alkaline-stable and high-performing polymer electrolyte materials has remained elusive until now. Despite vigorous research of AEM polymer design, examples of high-performance polymers with good alkaline stability at an elevated temperature are uncommon. Traditional aromatic polymers used in AEM applications contain a heteroatomic backbone linkage which is prone to degradation via nucleophilic attack by hydroxide ion.

In this presentation, I will highlight recent progress at the Bae group of Rensselaer Polytechnic Institute in the development of advanced hydroxide-conducting polymers and technology transfer effort to commercialize materials for AEM applications. We have developed new synthetic methods that produce polymer design made of all C−C bond backbone and a flexible chain-tethered quaternary ammonium group and that provide an effective solution to the problem of alkaline stability. The advantage of good solvent processability, synthetic versatility, and convenient scalability of the reaction process has generated considerable interest of these polymers, and they are considered leading candidates for commercial standard AEM. AEM fuel cells, electrolyzer, and vanadium redox flow battery tests of some of the developed polymer membranes showed excellent performance, suggesting that this new class of AEMs open a new avenue to electrochemical devices with real-world applications.
(Invited) Partially Fluorinated Anion Exchange Membranes for Electrochemical Applications
Authors: Miyatake Kenji , Kimura Taro , Inukai Junji , Uchida Makoto
Published: December 2020

There has been a considerable effort to develop high performance and durable anion exchange membranes (AEMs) for the electrochemical applications such as fuel cells, electrolyzers, and redox flow batteries. When these devices are operated under alkaline conditions, possible use of non-precious metal catalysts is advantageous. Although a number of AEMs have been proposed in the literature, chemical and mechanical stability in alkaline media still remains an issue for long-term, reliable operation of the devices. In the pursuit of more stable AEMs, we have recently reported some new polymer structures. Combination of absence of heteroatom linkages such as ether, sulfide, and sulfone in the main chain and employing pendant ammonium groups contributed to improvement of the alkaline and mechanical stability of AEMs. A typical example is QPAF-4 copolymers composed of perfluoroalkylene/phenylene main chain and hexylammonium head groups, which exhibited high hydroxide ion conductivity and alkaline stability.1

In the present paper, we report effect of other fluorinated components for our AEMs. We have developed a novel series of quaternized aromatic copolymers (BAF-QAFs) containing hexafluoroisopropylidene groups.2 Similar to QPAF-4 copolymer membranes, BAF-QAF copolymers had good solubility in polar organic solvents, membrane forming capability, and phase-separated morphology. Hexafluoroisopropylidene groups contributed to efficient anion transport as BAF-QAF membranes showed lower water uptake and higher hydroxide ion conductivity than those of QPAF-4 membranes. BAF-QAF membranes were thermally stable up to 95 °C and 90% RH with no obvious glass transition behavior in DMA analyses, while the elongation of BAF-QAF membranes were smaller than that of QPAF-4 membranes. BAF-QAF membranes were alkaline stable in 1 and 4 M KOH at 80 °C for 1000 h. A hydrogen/oxygen fuel cell with the BAF-QAF as a membrane and an electrode binder was successfully operated. The maximum power density reached 319 mW/cm2 at a current density of 702 mAcm2 with O2. The fuel cell with BAF-QAF copolymers were better in cathode performance than QPAF-4 cell most probably because of the higher hydroxide ion conductivity and better interfacial contact between the membrane and the catalyst layer.

Acknowledgements

This project was partly supported by NEDO through the Advanced Research Program for Energy and Environmental Technologies, JST through SICORP project, and JSPS/SNSF under the Joint Research Projects (JRPs) program.

References

Ono, T. Kimura, A. Takano, K. Asazawa, J. Miyake, J. Inukai, K. Miyatake, J. Mater. Chem. A, 5, 24804 (2017).

Kimura, A. Matsumoto, J. Inukai, K. Miyatake, ACS Appl. Energy Mater., 3, 469-477 (2020).

Figure 1
Electrochemical Synthesis of Polyaniline on Onion-like Carbon Nanoparticles Using the RoDSE Technique
Authors: Vargas Perez Brenda , Sanchéz Fonseca Fabiola Noemí , Gonzalez-Aponte Kattia Mitchelle , Cunci Lisandro
Published: December 2020

The world's main source of energy is fossil fuels, but fossil fuels are finite resources and can also irreparably harm the environment. According to the United States Energy Information Administration, the burning of fossil fuels was responsible for 76 percent of the US greenhouse gas emissions. Fossil fuels not only pollute the environment, but also affect human health. My research focuses on making a catalyst that is economical, efficient and above all friendly to the environment. The oxygen reduction reaction is an important reaction for energy conversion systems, such as fuel cells. The fuel cells generate electricity directly by electrochemically reducing oxygen and oxidizing fuel in water as the only by-product. Onion-like carbon (OLC) are used as a catalytic support for fuel cell applications due to their high conductivity and high surface-to-volume ratio. The combination of carbon compounds with conductive polymers results in new materials and devices with possible practical applications. In recent decades, several studies have been conducted on nitrogen doped structures in carbon materials for the oxygen reduction reaction. In my research we obtain OLC from nanodiamonds (ND) through a pyrolysis process. After this process, we oxidize the OLCs using sulfuric acid and potassium permanganate. These particles are then polymerized using the aniline and pyrrole monomers to dope the OLCs with nitrogen. These particles are characterized using the following techniques, Raman, Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). After characterizing them, the oxygen reduction reaction experiments are carried out. In the Raman, the characteristic bands of carbon materials were obtained, the D, G and double D bands. In the FTIR, vibrations of the C-N bonds were obtained at 1299 cm-1. In future works we will be adding to the particles nonprecious metals like cobalt and iron for oxygen reduction reaction, and characterize this samples using synchrotron techniques.
Improving Stability and Kinetics of Alkaline HOR Catalysts – Towards Reduced System Cost
Authors: Speck Florian Dominik , Ali Farhan S. M. , Paul Michael T. Y. , Singh Ramesh-Kumar , Böhm Thomas , Thiele Simon , Dekel Dario R. , Kallio Tanja , Cherevko Serhiy
Published: December 2020

Anion exchange membrane (AEM) fuel cells (FC) show great promise in overcoming monetary drawbacks of currently state of the art proton exchange membrane (PEM) FC, that rely on expensive Pt catalysts for both the hydrogen oxidation reaction (HOR) as well as the oxygen reduction reaction (ORR). With recent advancements in demonstrating high ORR activity and stability of Fe-N-C catalysts in alkaline environments,1 the HOR suddenly became the bottleneck reaction towards high power density platinum group metal (PGM) -low or -free AEM-FCs. While application of PGM-free ORR catalysts is an eventual goal, current state of the art NiM nanoparticles show relatively poor performance in terms of both activity and irreversible oxidation and dissolution.2 Hence, at least for some time, one will need to rely on PGM catalysts for alkaline HOR, where the biggest challenge will be lowering the loading and meanwhile increasing the stability in an alkaline environment. To this end, fundamental understanding of surface processes is required.

In this work we investigate model CeOx covered Pt and Pd electrocatalysts as benchmark materials for the HOR reaction.3,4 To prepare such model electrodes, we use physical vapor deposition and atomic layer deposition techniques for formation of PGM and a variable thicknesses CeOx surface layers, subsequently. Activity and stability of the CeOx@Pt and CeOx@Pd electrodes are studied in common rotating disk electrode (RDE) and on-line inductively coupled plasma mass spectrometry setups, respectively. External analytics, e.g. X-ray photoelectron spectroscopy (XPS), are used to further characterized the electrodes before and after degradation studies. We show that stability of the electrodes at the higher anodic potentials can be improved greatly by tuning the thickness of the CeOx layer. Interestingly, this can be achieved without sacrificing and even with a significant enhancement in the HOR activity. This unique performance is explained by assuming that the deposited CeOx films form an ion selective semipermeable passivation layer on the surface of Pd and Pt. We anticipate that as a next logical step such layers can be used to stabilize PGM free Ni alloys and reach the goal of having completely PGM-free FCs.

References

1. P. G. Santori, F. D. Speck, J. Li, A. Zitolo, Q. Y. Jia, S. Mukerjee, S. Cherevko and F. Jaouen, J. Electrochem. Soc., 166, F3311 (2019).

2. E. S. Davydova, F. D. Speck, M. T. Y. Paul, D. R. Dekel and S. Cherevko, ACS Catalysis, 6837 (2019).

3. N. M. Markovića, S. T. Sarraf, H. A. Gasteiger and P. N. Ross, J. Chem. Soc., Faraday Trans., 92, 3719 (1996).

4. H. A. Miller, F. Vizza, M. Marelli, A. Zadick, L. Dubau, M. Chatenet, S. Geiger, S. Cherevko, H. Doan, R. K. Pavlicek, S. Mukerjee and D. R. Dekel, Nano Energy, 33, 293 (2017).