bluuebunny/crossref_metadata_2025_split huggingface dataset:
Designing Cathode Layers for PEFC with the Low Platinum-Loading
Authors: Uda Keisuke , Noda Zhiyun , Nagayama Mayumi , Sasaki Kazunari , Hayashi Akari 
Published: February 2020

Introduction

Since the reduction of platinum-loadings in polymer electrolyte fuel cells (PEFCs) is essential for the further spread of their technology, many researchers have been working on this subject. Among those studies, the importance of controlling and optimizing structures of catalyst layers including the carbon frame has been reported for designing highly efficient PEFC with the low platinum-loading.1 In this study, membrane electrode assemblies (MEAs) with various platinum-loadings in the cathode are made and evaluated as a fundamental approach to reduce the platinum-loading. Then, we are trying to understand minimum requirement of platinum and to correlate resulting overvoltages with structures of cathode layers, and we are accordingly aiming to design highly efficient PEFC with the low platinum-loading.

Experimental

MEAs with various platinum-loadings in the cathode were prepared with 46% Pt deposited Ketjen black (TEC10E50E) and Nafion® by a spray printing method.2 Then, MEAs were evaluated in terms of impedance, IV performance, and ECSA. The thickness of catalyst layers were also measured by FIB-SEM. For further designing ideal electrocatalysts, electrocatalysts with different amounts of Pt deposition were made using Vulcan carbon as a carbon support and platinum(II) acetylacetonate as a platinum precursor through thermal reduction.3

Results and discussion

MEAs with the fixed anode (0.30 mgPt/cm2) and the varied cathodes (0.05 – 0.40 mgPt/cm2) have been prepared and evaluated in our study. Then, the minimum requirement of platinum in the cathode has been determined to 0.15 – 0.20 mgPt/cm2 through correlating the platinum-loading with activation overvoltage. Furthermore, the requirement of sufficient thickness of cathode layers has been found for reducing concentration overvoltage.4

In this report, the correlation between carbon amounts and concentration overvoltage was further evaluated by preparing MEAs with 0.05 – 0.60 mgPt/cm2 cathodes. Since decrease in the gas diffusion pathway by decreasing the cathode layer also leads to increase in the concentration of water produced by fuel cell reactions in the cathode layer, there should be the optimum thickness in terms of sufficient fuel diffusion. As a result, the optimum thickness was found to be 8.24 µm in this study. Since the importance of cathode thickness was realized for designing PEFC with the low platinum-loading, electrocatalysts with reduced Pt deposition on carbon were prepared in order to increase the cathode thickness even with reduced platinum-loadings. Consequently, successful reduction of concentration overvoltage was suggested from our experimental results. Obtained results will be explained more in details.
(1) M. Lee, et al., Electrochimica Acta, 56 (2011) 4783-4790.
(2) M. Okumura, et al., J. Electrochem. Soc., 164 (9), F928 (2017).
(3) A. Hayashi, et al., Electrochemica Acta, 53, 6117 (2008).
(4) K. Uda, et al., ECS Trans., 80 (8), 789 (2017).

Figure 1
Fe/N/C Cathode Catalyst Prepared from a Low Content of Fe Precursor to Obtain Atomically Dispersed Metal Center
Authors: Nabae Yuta , Nagata Shinsuke , Aoki Tsutomu , Tanida Hajime , Imai Hideto 
Published: February 2020

The development of Pt-free catalysts is strongly desired for globalization of proton exchange membrane fuel cells. Our research group has been developing Pt-free cathode catalysts obtained by pyrolyzing Fe containing polyimide nano-particles. While this sort of polyimide derived cathode catalysts shows very good performance, the structure of the Fe center was obscure. Furthermore, the previous synthesis of the catalysts started from a relatively large amount of Fe additives (2 wt%); therefore, extraordinary Fe species require to be washed out using HCl, the process of which was redundant.
In the present study, we tried to avoid the acid washing process by starting from a lower amount of Fe additives to simplify the synthetic procedure and increase the fraction of atomically dispersed Fe centers. Polyimide nano-particles were synthesized by the precipitation polymerization of pyromellitic acid dianhydride and 1,3,5-tris(4-aminophenyl)benzene with 0.3-0.5 wt% of Fe(acac)3 (acac = acetylacetonate). The Fe-containing polyimide precursor was heated at 600 °C for 5 h in a nitrogen atmosphere, and then heated again to 800 and 1000 °C for 1 h each in an ammonia atmosphere (50% balanced by nitrogen). Any acid washing was not performed during the whole synthetic procedure. The chemical composition of the resultant carbon was determined using a CHN elemental analyzer (PerkinElmer 2400-II) and an electron probe micro analyzer (Jeol JXA-8100): C 88.3 wt%, H trace, N 2.6 wt% and Fe 1.7 wt%. The Brunauer, Emmett and Teller (BET) surface area was determined to be 1360 m2 g-1 (Bel Japan Belsorp mini II).
Thus obtained Pt-free cathode catalyst was tested under H2-O2 fuel cell conditions. Figure 1 shows the I-V performance curves for the membrane electrode assembly (MEA) with the obtained catalyst. The measured and IR-free voltages at 2 A cm-2 reached 0.45 and 0.65 V, respectively; and the maximum power density was 0.89 W cm-2, suggesting the newly synthesized catalyst exhibits an extremely high performance as a Pt-free cathode catalyst.

Figure 1
Activity and Durability Insights for Atomically Dispersed (AD)Fe-N-C Oxygen Reduction Catalysts
Authors: Chung Hoon T , Cullen David A. , Yin Xi , Komini Babu Siddharth , More Karren L. , Myers Deborah J , Zelenay Piotr 
Published: February 2020

To reduce greenhouse gases (GHG) emission, we need to move away from fossil-based energy sources. Electrochemical energy conversion systems (EECSs), like fuel cells, are broadly considered to be alternative systems to the currently dominant internal combustion energy-generation systems (ICESs). Among several types of fuel cells, polymer electrolyte fuel cells (PEFCs) are the most suitable one for vehicle applications. Nanoparticle platinum (Pt) catalysts are now used as state-of-the-art catalyst for the PEFCs. However high price, scarcity, and monopolized global distribution of Pt place significant limitations on these energy conversion systems. Particularly oxygen reduction reaction (ORR) at the cathode is inherently slower by six orders of magnitude than hydrogen oxidation reaction at the anode, thus requiring higher Pt loading. Platinum group metal free (PGM-free) ORR catalyst development thus has been a continuous research theme for several decades by many research groups.
Metal-nitrogen-carbon (M-N-C) type catalysts have demonstrated the highest activity and durability among several types of PGM-free catalysts. Recently there has been a significant improvement in ORR activity, however further improvement in activity is still needed to compete with Pt catalyst. Furthermore good durability of these catalysts has not been demonstrated. Understanding of active site that has not been clarified yet is a core for solving these issues.
Recently we directly observed FeN4 moiety in (CM+PANI)-Fe-C catalysts [1]. If FeN4 is an active site for ORR, increasing the number of this moiety, i.e., making atomically dispersed (AD) Fe, will be a pathway for improving the ORR activity. Thus to achieve high density of FeN4, we synthesized fiber-type zeolitic imidazolate framework (ZIF-F) as a precursor for (AD)-Fe-N-C catalysts (Fig. 1 (a)), in which FeN4 structure already exist. Heat-treatment converts this ZIF-F into fibrous N-doped carbons (Fig. 1(b). Fe atoms are dispersed atomically without aggregation in the fibrous N-doped carbons (Fig. 1(c)). Importantly, electron energy loss spectroscopy (EELS) demonstrates that N is cordinated to the Fe atoms (Fig. 1(d)). Thus we could construct FeNx moieties within the (AD)-Fe-N-C catalysts.
In this presentation, we will present the activity and durability of this (AD)-Fe-N-C catalyst in rotating disk electrode (RDE) and fuel cells in conjunction with diverse analysis tools. This will give some insights for the nature of activity/durability for M-N-C type ORR catalysts.

Hoon T, Chung, David A. Cullen, Drew Higgins, Brian T. Sneed, Edward F. Holby, Karren L. More, Piotr Zelenay, “Direct atomic-level insignt into the active sites of a high-performance PGM-free ORR catalyst”, Science, 357, 479 (2017).

Acknowledgments

This research is supported by DOE Fuel Cell Technologies Office, through the Electrocatalysis Consortium (ElectroCat).

Figure 1
Wood-Based Carbon Materials Modified with Cobalt Nanoparticles As Catalysts for Oxygen Reduction and Hydrogen Oxidation
Authors: Tamasauskaite-Tamasiunaite Loreta , Norkus Eugenijus , Stagniūnaitė Raminta , Kepenienė Virginija , Sukackienė Zita , Niaura Gediminas , Drabavičius Audrius , Andrulevičius Mindaugas , Kruusenberg Ivar , Kaare Kätlin , Volperts Aleksandrs , Dobele Galina , Zurins Aivars 
Published: February 2020

In the present study, wood-based carbon materials were investigated as catalysts for the electro-reduction of oxygen (ORR) and electro-oxidation of hydrogen (HOR) in an alkaline medium. Activated wood-based carbon and black liqueur were doped with cheap nitrogen precursor, dicyandiamide (DCDA) and were modified with cobalt nanoparticles. The doping was done by pyrolysing samples at 800 °C in the presence of DCDA. The cobalt nanoparticles were deposited on the the N-doped wood-based carbon and N-doped black liqueur using morpholine borane as a reducing agent. The synthesized catalysts were characterized using TEM, XPS, Raman Spectroscopy and ICP-OES. For electrochemical measurements, the glassy carbon (GC) electrodes were modified with synthesized catalysts and the experiments were carried out in 0.1 M KOH solution employing rotating disk electrode (RDE) method. For modifying the electrodes, a suspension (4 mg ml–1) was made in 2% polyvinylidenefluoride in N-methyl-2-pyrrolydone solution.
It was found that the N-doped wood-based carbon and N-doped black liqueur samples modified with cobalt nanoparticles show good activity for oxygen reduction and hydrogen oxidation. The combination of metal nanoparticles and N-doped wood-based carbon and N-doped black liqueur opens up new possibilities for design of the next generation catalysts.

Acknowledgment

This research was funded by a grant (M-ERA.NET-1/2016) from the Research Council of Lithuania. The author’s research was performed in cooperation with the University of Tartu (Estonia), Latvian State Institute of Wood Chemistry (Latvia) and Horizon Pulp&Paper Ltd (Estonia) under the M-ERA.NET 2 project “Wood-based Carbon Catalysts for Low-temperature Fuel Cells (WoBaCat)“ (reg. No. project3213).
Nitrogen Doped Graphene with High Performance for Oxygen Reduction Reactions
Authors: Li Shanshan , Shi Zhihao , Chen Yingjie , Yu Liyan , Dong Lifeng 
Published: February 2020

Nowadays, ever-growing demand for fuel cells has inspired great effort to seek alternative cathode materials to replace current commercial Pt/C catalyst. Spinel catalysts with low cost and adjustable properties revealed fascinating prospects. Unique nanostructures were designed to increase active sites, facilitate kinetics, and decrease mass transport resistance. Meanwhile, both direct and mediate coupling between Ag and MFe2O4 were proposed to enhance their catalytic activities. Furthermore, different conductive matrixes such as graphene, carbon nanotube and fiber have been utilized as support for these materials to improve conductivity. Heteroatoms such as N and S introduced into graphene lattice were proposed to transfer neighboring carbon atoms to “active regions” with enhanced catalytic activity. The integration of metal oxide nanoparticles with heteroatom-doped graphene demonstrated superior oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities. However, as to the deposition of dumbbell nanocomposites on N or S doped graphene, binding to different components might introduce different electron transfer and active sites.
Herein, Ag-MnFe2O4 nanoparticles were synthesized and deposited on N-doped graphene (N-rGO) and S-doped graphene (S-rGO), respectively. According to their reduction peaks, N-rGO demonstrated higher catalytic activity than S-rGO. Moreover, Ag-MnFe2O4 nanoparticles on N-rGO (Ag-MnFe2O4/N-rGO) showed more enhanced effects than those particles on S-rGO (Ag-MnFe2O4/S-rGO). Thus, Ag-MnFe2O4/N-rGO can be developed to replace Pt for ORR.
Multiblock Anion Conducting Copolymers Based on Vinyl Addition and Ring-Opening Metathesis Polymerization of Norbornenes
Authors: Mandal Mrinmay , Huang Garrett , Kohl Paul A 
Published: February 2020

Anion-exchange membranes (AEMs) have widespread applications in electrochemical devices. The development of AEMs with long-term alkaline stability and high hydroxide ion conductivity is currently of interest. The use of non-precious catalysts, facile reaction kinetics and reduced fuel crossover are some of the benefits over proton-exchange membranes (PEMs). However, the present limitations of AEMs include low ionic conductivity, poor stability at high pH, and high water uptake.
A series of multiblock copolymers based on vinyl addition and ring-opening metathesis polymerization (ROMP) of norbornenes was synthesized for use in AEM fuel cells and electrolyzers (Scheme 1). The mechanical and thermal stability, ionic conductivity of both sets of polymers are discussed in detail. The long-term (>1200 h) alkaline stability results are promising.
Financial support provided by the ARPA-E IONICS program for M.M. and G.H. is gratefully acknowledged.

Figure 1
P2G System Technology Development Aiming at Building a CO2-Free Hydrogen Society
Authors: Sakamoto Masaki , Izuhara Daisuke , Sotouchi Hiroko , Aoyagi Fukuo 
Published: February 2020

The government's "Basic Energy Plan" decided on April 11, 2014 has been decided to promote initiatives aimed at realizing "hydrogen society", a society that utilizes hydrogen in everyday life and industrial activities It was. Following this, the Ministry of Economy, Trade and Industry will formulate the "Hydrogen / Fuel Cell Strategy Roadmap" in June 2014 and aim to establish a CO2-free hydrogen supply system around the year 2040.
According to the Government's "Long-Term Energy Supply and Demand Outlook" published in July 2015, the renewable energy ratio to total electricity generation in FY 2030 is estimated to be 22 to 24%. On the other hand, renewable energy has large output fluctuations due to the influence of the natural environment, and geographically unevenly, there are concerns such as suspension of connection to the transmission and distribution electric power network. One solution to this problem would be the Power-to-Gas system utilizing the conversion using electric power from renewable energy into hydrogen. The obtained hydrogen can reduce CO2 emissions by replacing fossil fuels in heating sector.
At the Agency for Natural Resources and Energy, the report of the "CO2 Free Hydrogen Working Group" was compiled in March, In the report, technical issues such as low cost and high efficiency of various technologies including water electrolysis equipment, improvement of durability, improvement of utilization rate were taken as technical issues.
In this research, we demonstrate technological development from hydrogen production using renewable energy to transportation, storage and use in the real society, and establish the basic technology for practical application of "Power to Gas system".

ACKNOWLEDGEMENT

This work was partially supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.
Highly Accelerated Mass Transport within Jungle-Gym-Type Ir Electrocatalyst for Water Electrolyzers
Authors: Kim Ye Ji , Jung Yeon Sik 
Published: February 2020

Hydrogen is an efficient and clean energy carrier, as well as a fuel for transportation and various other applications. Polymer electrolyte membrane water electrolysis (PEMWE) has shown to be a promising method for producing pure hydrogen without significant additional compression.[1] However, understanding the relationship between nanostructure and activity is one of the current challenges faced by water electrolysis for analyzing and improving IrOx-based catalysts for the OER. Herein, in order to confirm the effect of controlling the nanostructure, jungle-gym-structured Ir OER catalysts were fabricated using solvent-assisted nanotransfer printing (S-nTP). They are composed of vertically stacked nanowire array with a periodicity. They showed 4 higher mass activity than that of iridium black powder(2-4 nm in diameter). To measure the electrochemically active surface area, the integrated surface charge was calculated from the cyclic voltammetry in the range of 1.0 – 1.4 V vs RHE. The jungle-gym-type Ir catalyst recorded 2.3 times higher integrated surface charge compared to that of iridium black powder. If the mass activity is normalized by the integrated surface charge, turnover frequency (TOF) can be calculated, which is associated with the specific current density per electrochemically active surface area. [2] TOF values 1.8 times higher than iridium black were observed in the case of jungle-gym-structured one. The efficiency of the catalyst utilization has been maximized due to the novel structure, achieving a high ratio of surface area to the mass of the structure as high as that of Ir Black catalysts. Moreover, the jungle-gym nanostructure within the catalyst layer enhanced the intrinsic activity of the catalyst due to the accelerated mass transport within the catalyst layer.
Reference
[1] Aricò, A. S., et al. "Polymer electrolyte membrane water electrolysis: status of technologies and potential applications in combination with renewable power sources." Journal of Applied Electrochemistry2 (2013): 107-118.
[2] Abbott, Daniel F., et al. "Iridium oxide for the oxygen evolution reaction: correlation between particle size, morphology, and the surface hydroxo layer from operando XAS." Chemistry of Materials18 (2016): 6591-6604.
On the Effect of Bipolar Plate Mechanical Properties on the Current Distribution of Proton Exchange Membrane Water Electrolysis
Authors: Al Shakhshir Saher , Zhou Fan , Kær Søren Knudsen 
Published: February 2020

The durability and lifetime of the proton exchange membrane water electrolysis (PEMWE) is directly affected by the current distribution (CD). Uniform CD indicates uniform electrochemical reaction and vice versa. CD of PEMWE is affected by many factors, such as flow field patterns, catalyst particle distribution in the catalyst layer, and the contact between different components of PEMWE, especially between the bipolar plates and the current distribution plate. The mechanical properties of the bipolar plate such as the ductility and bristliness might affect the current distribution significantly. In this work, the CD is measured at the cathode side using S++ setup, where the segmented plate is placed between the current distributor and bipolar at the cathode side of the PEMWE cell. The segmented plate consists of 100 segments over the 50 cm2, thus each segment area is 0.5 cm2. Two different materials (graphite and Titanium) for the bipolar plates are used in this work, to investigate the effect of bipolar plate mechanical properties on the CD of the PEMWE.
Initial results show that, the PEMWE with titanium flow field plate has shown a non-uniform CD at higher clamping pressure, and a more uniform CD at lower clamping pressure. Meanwhile, the PEMWE with graphite flow field plate has shown a highly uniform CD at higher torque and a less uniform CD at lower torque. Also, it is concluded that higher PEMWE cell performance not necessary means more uniform CD over PEMWE active area.

Figure 1
Two Phase Flow Modeling and Characterization of Oxygen Bubbles in PEM Water Electrolysis Cells
Authors: Nouri-Khorasani Amin , Kwan Jason Tai Hong , Bonakdarpour Arman , Wilkinson David P. 
Published: February 2020

The formation, growth, and stability of oxygen bubbles inside the porous transport layer (PTL) pores of a polymer electrolyte membrane water electrolysis (PEMWE) cell have been modeled. In a PEMWE cell, O2 bubbles form and grow inside the anode catalyst layer (ACL) and PTL pores. The most critical impact of the O2 bubbles on the overall performance is the screening of the ACL surface. Semi-empirical relations for the current density-surface coverage for gas evolving electrodes have previously been developed [1] and were used for our PEMWE modeling [2]. This screening effect has been evaluated as an overpotential term, and the results were used to predict the effects of the catalyst and PTL properties on the electrolysis cell performance. The fluctuations in the cell current density were used to identify different types of bubbles and their detachment frequency from the anode electrode.
In this work, the anode catalyst surface has been described as a smooth, planar and horizontal plane. The PTL pores are described as identical straight hydrophilic cylinders with 1-mm height. Such a structure resembles tunable PTL structures such as those synthesized by Kang et al. [3]. Stable O2 bubble nuclei form mainly at the intersection of the anode catalyst layer and the PTL pore wall [3,4].
Our modeling results show the effects of three different types of bubbles in a PEMWE cell: i) nucleation-driven, ii) drag-driven, and iii) buoyancy-driven bubbles. Figure 1 shows the relative lifetime and overpotential effects of the O2 bubbles in a PEMWE with a PTL consisting of 11 μm dia. pores operated at a fixed temperature of 80°C and a balanced pressure of 1 bar [5]. Comparing the current density fluctuations in chronoamperometry experiments with the bubble detachment frequencies obtained through modeling provides a distribution of different types of bubbles in the electrolysis cell. These frequencies vary according to the PTL structure and the PEMWE cell operating conditions. Understanding of bubble growth and detachment mechanisms are of significant importance for reduction of mass transport-related losses and enhancement of PEMWE performance.

References:

H. Vogt and K. Stephan, Electrochim. Acta, 155, 348–356 (2015).

E. Tabu Ojong et al., Int. J. Hydrogen Energy,
42
, 25831-25847 (2017).

Z. Kang et al., Energy Environ. Sci., 10, 166-175 (2017).

O. F. Selamet et al., Int. J. Hydrogen Energy, 38, 5823–5835 (2013).

A. Nouri-Khorasani, E. Tabu Ojong, T. Smolinka, and D. P. Wilkinson, Int. J. Hydrogen Energy, 42, 28665–28680 (2017).

Figure 1