bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability Design Principles of Mn-Based Oxides for Acidic Electrolytes
Authors: Peng Jiayu , Giordano Livia , Davenport Timothy , Shao-Horn Yang 
Published: December 2020

Manganese-based oxides are promising, earth-abundant candidate materials in many electrochemical energy applications in aqueous environments, including supercapacitors,1 electrocatalysis2 and solar fuels.3 The use of these oxides in acidic systems, such as proton-exchange membrane fuel cells and electrolyzers,4,5 is, however, severely limited by the bulk instability of Mn oxide phases according to their Pourbaix diagrams.2 Designing active and stable Mn-based oxide catalysts in acidic electrolytes therefore requires fundamental understanding towards their aqueous stability and dissolution mechanism in acid.
In this study, we systematically examined the aqueous stability of Mn-based oxides with a diverse range of chemistry, structures and oxidation states in acidic electrolytes. Decreasing the metal-oxygen covalency, e.g. by having Mn ions with lower nominal oxidation states, was found to weaken the manganese-oxygen bonds, reduce the energy penalty for the formation of Mn vacancies and subsequent ion solvation, rendering poorer stability in acidic solutions. Moreover, we identified the critical role of oxide acid-base chemistry6 in dictating the stability of Mn-based oxides, where lifting up the Fermi levels on the absolute energy scale by decreasing covalency can lead to greater thermodynamic driving force for the surface protonation of these metal oxides, which further weakens the surface metal-oxygen bonds and contributes to the instability of Mn-based oxides in acidic electrolytes. This work highlights the importance of understanding the physical origin of the aqueous stability trends for metal oxides with electronic and/or energetic descriptors, and provides guiding principles for designing oxide catalysts with enhanced stability in acidic systems.
References:
1. J. T. Mefford, W. G. Hardin, S. Dai, K. P. Johnston, K. J. Stevenson, Nat. Mater. 2014, 13, 726.
2. K. A. Stoerzinger, M. Risch, B. Han, Y. Shao-Horn, ACS Catal. 2015, 5, 6021.
3. A. Shinde, S. K. Suram, Q. Yan, L. Zhou, A. K. Singh, J. Yu, K. A. Persson, J. B. Neaton, J. M. Gregoire, ACS Energy Lett. 2017, 2, 2307.
4. R. Frydendal, E. A. Paoli, I. Chorkendorff, J. Rossmeisl, I. E. L. Stephens, Adv. Energy Mater. 2015, 5, 1500991.
5. L. Zhou, A. Shinde, J. H. Montoya, A. Singh, S. Gul, J. Yano, Y. Ye, E. J. Crumlin, M. H. Richter, J. K. Cooper, H. S. Stein, J. A. Haber, K. A. Persson, J. M. Gregoire, ACS Catal. 2018, 8, 10938.
6. J. Portier, P. Poizot, G. Campet, M. A. Subramanian, J. M. Tarascon, Solid State Sci. 2003, 5, 695.
(Invited) Promising Methods for Overcoming Trade-Offs Among Catalytic Activity, Durability, and Power Density By Controlling Pt/Ionomer Interfaces
Authors: Kodama Kensaku , Yamada Haruhiko , Yoshino Shuhei , Kudo Kenji , Suzuki Takahisa , Shinohara Akihiro , Jinnouchi Ryosuke , Morimoto Yu 
Published: December 2020

For improving the efficiency and reducing Pt use in polymer electrolyte fuel cells, it is essential to improve the catalytic activity per Pt mass for oxygen reduction reaction (ORR) in the cathode. In addition, recent studies have demonstrated that a high surface area of the catalyst per Pt mass is necessary for reducing the oxygen transport resistance in the catalyst layer. Alloying inner cores of nanoparticles by introducing base metals and reducing particle sizes are established methods to increase the mass activity and the surface area, respectively. Both the methods are, however, disadvantageous for the catalyst durability. Thus, the activity, durability, and power density are generally in trade-off relations.
A promising method for solving this problem is to change the properties of the surrounding rather than the catalyst itself. Ionomers adsorbed on Pt catalyst have been confirmed to inhibit ORR and oxygen permeation to the interface [1, 2]. In other words, both the reaction and permeation can be promoted without deteriorating the catalyst durability by mitigating the ionomer adsorption. We have indeed shown that the ionomer adsorption can be suppressed by modifying the molecular structure of ionomer [3]. The ionomer adsorption can be suppressed also by inserting a sub-nanometer thin porous carbon layer between the Pt surface and ionomer. The inserted carbon layer has been also shown to suppress the catalyst degradation during potential cycles [4].
In this talk, we first summarize our analytical works on Pt/ionomer interfaces, focusing on the mechanisms of the adsorption of anionic moieties in ionomers and its effect on ORR. Then, we discuss the effectiveness of various approaches for mitigating ionomer adsorption, as well as their limitations. The future direction of cathode catalyst developments is also discussed.
[1] Subbaraman et al., ChemPhysChem 11, 2825 (2010).
[2] Jinnouchi et al., Electrochim. Acta, 188, 767 (2016)
[3] Kodama et al., ACS Catal. 8 694 (2018).
[4] Yamada et al., J. Electrochem. Soc., in press.
Effect of the Pore Structure of the Gas Diffusion Electrode on the Power Generation and Mass Transport Properties of Direct Formic Acid Fuel Cell
Authors: Tsujiguchi Takuya , Osaka Yugo , Kodama Akio 
Published: December 2020

Direct Formic Acid Fuel Cell has been attracted match attention due to its higher power density and lower crossover. In order to improve their performance, we have tried to improve the mass transport in the anode electrode since a large amount of carbon dioxide is emitted by the electrochemical reaction.
For the anode electrode, diffusion layer, such as carbon cloth and carbon paper used in the polymer electrolyte fuel cell, is commonly used in direct formic acid fuel cell. These diffusion layers were suitable for the gas supplying; however, it is not clear that these diffusion layers were also suitable for direct liquid fuel cell using liquid fuel. Moreover, the suitable pore structure of diffusion layer for the direct liquid fuel cell is also unknown. In this context, we fabricated the gas diffusion layer having different pore diameter, thickness and porosity using same manner and material in order to evaluate the effect of the pore structure of diffusion layers on the power generation characteristics and mass transport properties in direct formic acid fuel cell.
The diffusion layers having 0.03-0.1 mm in average pore diameter, 60-90% in porosity, and 0.1-0.3 mm in thickness could be successfully fabricated using the purchased carbon fiber. The direct formic acid fuel cells using different diffusion layers for anode were fabricated and evaluated the i-V performance and crossover flux. It was found that the big pore can enhance the fuel feed rate to the anode catalyst layer under low current density (low CO2 emission), on the other hands, it did not contribute to the improvement of the fuel feed rate to the catalyst layer under higher current regions (high CO2 emissions). Small pore showed the counter trend. These results implies that the liquid feed and CO2 emissions is closely related the pore properties of diffusion layers, therefore, it is suggested that diffusion layer having suitable pore properties for direct liquid fuel cell is desired.
Effect of Varying Carbon Supports on Pt Based HOR Electrocatalysts for Alkaline Media Synthesized By CVD
Authors: Williams Stefan T. D. , Rockward Tommy , Martinez Ulises , Zawodzinski Thomas A. 
Published: December 2020

The synthesis of electrocatalysts for the chemical reactions of hydrogen systems (e.g. fuel cells and electrolyzer systems) continues to be a significant area of research in the renewable energy community. The kinetics of hydrogen reactions decrease by two orders of magnitude in alkaline environments compared to acidic, which has rendered significant challenges in the development as catalysts of alkaline fuel cell systems[1,2]. Chemical vapor deposition (CVD) is a conventional synthesis process applied to manufacture electrocatalysts[3,4]. In this study, a modified form known as “Poor Man’s” CVD (PMCVD) is utilized, to further its impact in electrochemical catalyst development. This work assesses the deposition mechanism as well as its ability to develop tuneable catalysts for the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) for alkaline media.
In our last efforts, we showed Pt based catalysts synthesized using the PMCVD method exhibited higher activities for the HOR/HER in alkaline media than commercially available catalysts[5]. The performance was attributed to the tunability of crystallite size by varying the temperature and pressure of the PMCVD process. In an effort to further understand the deposition mechanism of this processes, we investigated Pt catalysts on various carbon supports. In doing so, Pt was deposited on three supports: XC-72, Acetylene Black, and Graphitized Nanoplatelets with 30% Pt by weight. The carbons varied in both surface areas and degree of graphitization. This work will summarize the HOR/HER activities of these three Pt/C catalysts in alkaline media. It will also help elucidate the impact of the deposition mechanism as a function of each support based on their material properties.
[1] Durst, J. et al. New insights into the electrochemical hydrogen oxidation and evolution reaction mechanism. Energ. Environ. Sci. 7, 2255–2260 (2014).
[2] Sheng, W. et al. Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes.” Electrochem. Soc. 2010 volume 157, issue 11, B1529-B1536
[3] Garcia, Vargas, et al., “Chemical Vapor Deposition of Iridium, platinum, Rhodium, and Palladium.” Materials Transactions, Vol. 44, No. 9 (2003) pp. 1717 to 1728
[4] Serp, Philppe, et. al., “Chemical Vapor Deposition Methods for the Controlled Preparation of Supported Catalytic Materials.” Chem. Rev. 2002, 102, 3085−3128
[5] Williams, S. et. al. “Synthesis and Characterization of Electrocatalysts for the Hydrogen Evolution Reaction in Alkaline Environment.” ECS Abstract Fall 2019.

Figure 1
Polymer-Ceramic Composite Diaphragm for Reducing Dissolved Hydrogen Permeability in Alkaline Water Electrolysis
Authors: Lee Hae In , Cho Hyun-Seok , Kim Sang Kyung , Kim MinJoong , Kim Chang-Hee , Cho Won-Chul , Rhee Young Woo 
Published: December 2020

The porous diaphragm is a typical separator used in an alkaline water electrolyser. Gas crossover through the diaphragm during electrolysis depends upon the different evolution quantity of hydrogen and oxygen gas which consequently develop the differential pressure between cathode and anode side. This phenomenon limits the cell efficiency and develops safety concerns. In this study, diaphragm was prepared by film casting, which consists of mixing, casting and extraction. We measured the hydrogen flux density of commercial diaphragm (Zirfon PERL) and the prepared diaphragm during the operation. For this purpose, the diaphragm was mounted in a zero-gap design unit cell with Ni foam as electrodes and operated in 30wt% KOH solution at 60oC with atmospheric differential pressure between 0.1 ~ 0.3 bar (cathode side – anode side) controlled by a back-pressure regulator. Results showed that the anodic hydrogen content of commercial diaphragm was up to 2% during the operation but prepared diaphragm was negligible. This is due to the smaller pore size in the prepared diaphragm as compared to the commercial diaphragm confirmed by morphological and surface area analysis.
Fig 1. (a) The anodic hydrogen contents as a function of current density and differential pressure and (b) polarization curves at 60oC and 30wt% KOH solution of conventional and prepared diaphragm with nickel foam as electrode

Figure 1
New Strategies to Strongly Coupled Ni-Molybdenum Carbide Grafted N-Doped Carbon Architectures for Efficient Electrocatalysis
Authors: Das Debanjan , Santra Saswati , Nanda Karuna Kar 
Published: December 2020

Despite the recent promise of transition metal carbides as non-precious catalysts for hydrogen evolution reaction (HER), their extension to oxygen evolution reaction (OER) in order to achieve the goal of overall water splitting remains a significant challenge. Herein, a new Ni/MoxC (MoC, Mo2C) nanoparticles supported N-doped graphene/CNT hybrid (NC) catalyst is developed via a facile, one-step integrated strategy which can catalyze both the HER and OER in an efficient and robust manner. The catalyst affords low overpotentials of 162 and 328 mV to achieve a current density of 10 mA/cm2 for HER and OER, respectively, in an alkaline medium which either compares favourably or exceeds most of the Mo-based catalysts documented in the literature. The electronic synergistic effect between MoxC, Ni and NC are responsible for the higher electrocatalytic activity wherein, a tandem electron transfer process yields both excellent HER and OER activity. [1]
Unfortunately, however, the synergy among the components was curtailed on account of large spatial separation. To mitigate this problem, we pyrolyzed a PANI/NiMoO4 nanowire hybrid which brought the individual components closer as compared to the previously adopted method resulting in improved catalytic activity. To further enhance the intimacy in these multi-component catalysts, a MOF-confined synthesis method was developed which resulted in the best activity among all the catalysts developed in the series.
[1] D.Das, S.Santra and K.K Nanda, ACS Appl. Mater. Interfaces, 2018, 10, 35025−35038
Thermo-Chemically Durable Perfluorinated Anion-Conducting Ionomer Membranes for Advanced Alkaline Water Electrolysis
Authors: Nguyen Quynh-Mai , Jung SungYoon , Hwang Jin Pyo , Jang Wongi , Lee Chang Hyun 
Published: December 2020

The state-of-the-art membrane for alkaline water electrolysis is porous Zirfon®. Unfortunately, Zirfon® has been suffering from the crossover of hydrogen gas permeated through the pores, inducing safety issues including explosion. To date, there have been approaches to solve this problem. One good example is to use anion-conducting ionomer membranes with dense structures. Generally, the membranes, which are made up of hydrocarbon matrices, experience severe degradation, when they are exposed under strong basic conditions at the temperatures higher than 50 oC for high electrochemical performances. In this study, perfluorinated ionomer membranes with extremely high thermo-chemical resistances are developed via the combination of architectural design and supercritical dispersion.

References

[1] Zirfon perl separator for alkaline water electrolysis, AGFA, April (2016)
[2] C. Y Ahn, J, Ahn, S. Y. Kang, O. H. Kim, D. W. Lee, J. H. Lee, J. G. Shim, C. H. Lee, Y. H. Cho, Y. E. Sung, Sci Adv
6, 1-9 (2020)

Keywords: Alkaline water electrolysis, Perfluorinated ionomers, Anion conductivity, Thermo-chemical stability, Membrane
Visualization of Bubble Behavior on Hydrophobic Coated CL in PEM Water Electrolysis Cell
Authors: Wani Kodai , Araki Takuto , Nagasawa Kensaku , Mitsushima Shigenori 
Published: December 2020

Due to the need for a new energy infrastructure, water electrolysis technology is receiving increased attention (1), (2). One of the serious problems is management of generated oxygen bubbles which inhibit water supply to the CL. Therefore, bubble behavior was observed on three types of CL with hydrophilic and hydrophobic surface by using a high-speed camera. A single cell, shown in Fig. 1, was used for observing oxygen bubble behavior. Nafion-117 was used as PEM, and IrOx and Pt/C was used anode and cathode catalyst, respectively. Sinterd Ti with Pt plating was used for anode porous transport layer (PTL). Three types of PTFE coated CL were prepared: (a) no coating, (b) coated all and (c) coated half. High-speed camera (Redlake MASD, HS-1), magnifying glass (Hirox, cx-10c) and objective lens (Hirox, OL-35) were used. Electrochemical measurement system (Bio-Logic, SP-240) was used for applying voltage, and the voltage sweep was performed at a rate of 4 mV/s until the cell voltage turned from 0 V to 2.5 V. The current density at voltage of 2.5 V was about 4200 mA/cm2 for CL (a), 1200 mA/cm2 for CL (b) and 3700 mA/cm2 for CL (c). A big bubble covering entire PTL hole was visualized in Fig. 2 (b). In Fig. 2 (c), smaller bubbles appeared from left PTFE uncoated area were merged into a bigger bubble, which stayed on right PTFE coated area. The size of bubbles staying on the edge of PTL-holl in Fig. 2 (a) was smaller than those of (b, c). The results may suggest that the CL (b) deteriorated the cell performance because of the bubble covering entire reaction area. From this experiment, we could control stagnation of bubbles on CL by PTFE treatment. There may be some possibilities that controlling bubble stagnation make some differences on cell performance.
Acknowledgements: This study was based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO).
Reference:
(1) G. Bender, et al, Int. J. Hydrogen Energy, 44 (2019), 9174-9187
(2) S. Mitsushima et al, ECS Meeting Abstracts, MA2019-02 (2019), 1715.

Figure 1
Direct Roll-to-Roll Coating of Catalyst-Coated Membranes for Low-Cost PEM Water Electrolyzers
Authors: Park Janghoon , Kang Zhenye , Bender Guido , Ulsh Michael , Mauger Scott A 
Published: December 2020

Low temperature polymer electrolyte membrane (PEM) water electrolysis is a technology capable of producing hydrogen, which has been in the spotlight with the recent worldwide efforts to improve energy system sustainability and security. As the drive toward megawatt-scale hydrogen production intensifies, the production rate of PEM water electrolyzers is becoming an important issue. Catalyst-coated membranes (CCM) are a key component of water electrolyzers. However, existing spray coating and decal transfer methods have several limitations with regards to large-area production of the CCMs, such as, slow production speeds and multiple process steps.
In this talk, high-throughput and large-area CCM production based on roll-to-roll (R2R) slot-die coating of IrO2 catalyst inks directly onto the membrane will be discussed. In order to minimize phenomena such as swelling and solvent permeation during direct coating of the ink onto the membrane, ink compositions with various catalyst contents, types of organic solvents, and water-to-solvent ratios are investigated. The results show that alcohol-rich inks may lead to improved particle dispersion and wetting onto the substrate, but have shown poor coating qualities (e.g. cracks and high thickness deviation) due to larger ink-membrane interaction and faster drying rate. In-situ results of R2R-processed CCMs using optimized inks will be presented that indicate comparable electrochemical performance to a lab-scale sample fabricated with the standard ultrasonic spray coating technique. Considering that the R2R-processed CCM has achieved a throughput of several hundred times greater than the lab scale sample (on an area/time basis), it is expected that this manufacturing approach can contribute to a significantly reduced capital cost of PEM water electrolyzers.
This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Hydrogen and Fuel Cells Technologies Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.
Gas Phase Electrolysis of Anhydrous HCl for Dry H2 Production
Authors: Likit-anurak Kris , Brizes Michael , Shimpalee Sirivatch , Lopata Joseph Steven , Weidner John W. , Murdock Laura , Benicewicz Brian C , Meekins Benjamin 
Published: December 2020

Chlorine (Cl2) is an important feedstock used in a variety of industry processes [1]. Hydrogen (H2) and chlorine gas (Cl2) can be produced by the electrochemical oxidation of hydrogen chloride (HCl) anhydrous gas. Previously, a gas phase hydrogen bromine (HBr) electrolyzer showed better performance than aqueous phase due to a significant increase in reactant diffusion rate [2-5]. Furthermore, sulfonated polybenzimidazole (s-PBI) membranes have shown promising performance in this application because they can be operated in strong acid environments and at high temperature [6].
The propose of this work was to elucidate the role of the polymer membrane, the efficiency and durability of cathode catalyst (Pt vs IrRuOx), and the optimal operating parameters (temperature, flow rate, and cell potential). We found that the s-PBI gel membrane doped in 50 wt% H2SO4 showed significantly better performance than NafionTM membranes, regardless of their thickness, due to a reduction in membrane resistance and a decrease in chloride ion crossover. We considered as well how crossover of Cl- from anode to cathode can poison the cathode catalyst, affecting the durability of the electrolyzer. We also discuss how the cell temperature and HCl flow rate affect the performance of the electrolyzer, with a focus on reducing the cell potential required to electrolyze HCl by increasing the reaction temperature.
References:
[1] The American Chemistry Council (ACC). “2017 Elements of the Business of Chemistry” NE Washington, DC: [Online] Available: https://www.americanchemistry.com/2017-Elements-of-the-Business-of-Chemistry.pdf
[2] B. Huskinson, J. Rugolo, S.K. Mondal, M.J. Aziz, Energy & Environmental Science. 5 (2012) 8690.
[3] F. Mohammadi , S.N. Ashrafizadehb, A. Sattari, Chemical Engineering Journal 155 (2009) 757–762.
[4] V. Barmashenko and J. Jo"Rissen, Journal of Applied Electrochemistry 35 (2005) 1311–1319
[5] P. Sivasubramanian, R.P. Ramasamya, F.J. Freireb, C.E. Hollanda, J.W. Weidner, International Journal of Hydrogen Energy 32(4) (2007) 463-468.
[6] T. R. Garrick, C. H. Wilkins, A. T. Pingitore, J. Mehlhoff, A. Gulledge, B. C. Benicewicz, J. W. Weidner, J. Electrochem. Soc. 2017, 164(14), F1591-F1595
Three-Dimensional, Two-Phase Computational Fluid Dynamics Simulations of Alkaline Diaphragm Water Electrolysis Devices
Authors: Lopata Joseph Steven , Kang Sanggyu , Cho Hyun-Seok , Kim Chang Hee , Shimpalee Sirivatch 
Published: December 2020

Alkaline diaphragm water electrolysis (ADWE) devices are the most widely commercialized water splitting cells for large-scale applications. They are inexpensive and durable, but they undergo numerous voltage loss mechanisms that are absent in ion-exchange cells.1 Computational studies enable us to understand these losses and to engineer components that diminish them. Hammoudi et al.2 developed a validated one-dimensional multi-physics model incorporating bubble effects and compared relative overpotentials at different temperatures. Abdin et al.3 used a multi-physics approach that included electrode and separator properties to show effects of design parameters on performance.
Our aim is to utilize computational fluid dynamics techniques to build an ADWE model that enables us to effectively engineer the flow field and porous transport layer (PTL). This two-phase model considers losses due to the presence of bubbles in the electrolyte, bubbles on the electrode surface, and shunt current through the diaphragm. We include a discussion of the current distribution in a straight channel ADWE device and what factors are important to consider for optimizing productivity and efficiency.
References:

M. Schalenbach et al., Journal of The Electrochemical Society, 163, F3197–F3208 (2016).

M. Hammoudi, C. Henao, K. Agbossou, Y. Dubé, and M. L. Doumbia, International Journal of Hydrogen Energy, 37, 13895–13913 (2012).

Z. Abdin, C. J. Webb, and E. M. A. Gray, Energy, 138, 316–331 (2017).