bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fabrication of Flexible Catalysts for Hydrazine Electro-Oxidation
Authors: Zabielaite Ausrine , Šimkūnaitė-Stanynienė Birutė , Šimkūnaitė Dijana , Naruškevičius Leonas , Vaičiūnienė Jūratė , Tamašauskaitė-Tamašiūnaitė Loreta , Norkus Eugenijus 
Published: December 2020

In this study, we report a facile electrochemical approach for fabrication of flexible catalysts for the electro-oxidation of hydrazine with the aim to use them as the anode material in direct hydrazine fuel cells (DHFCs). A fiber-shaped cobalt coating has been electroplated on the copper coated polyimide surface (labeled as Cofiber/Cu/PI) using the electrolyte containing CoSO4, NaOH and N-(2-Hydroxyethyl) ethylenediamine. For comparison, the cobalt layer that has the smooth structure has been also electrodeposited on the flexible Cu/PI surface (labeled as Cosmooth/Cu/PI). Additionaly, the fabricated flexible catalysts have been decorated with gold (Au), manganese (Mn) or gold-manganese (AuMn) nanoparticles via electrochemical deposition. The morphology, structure and composition of the fabricated flexible catalysts have been characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and inductively coupled plasma optical emission spectroscopy. The activity of catalysts has been investigated with respect to the electro-oxidation of hydrazine in an alkaline medium using cyclic voltammetry and chrono-techniques.
It was found that the deposition of Au, Mn or AuMn nanoparticles on Cofiber/Cu/PI and Cosmooth/Cu/PI results in significantly enhanced electrocatalytic activity of Cofiber/Cu/PI and Cosmooth/Cu/PI towards the electro-oxidation of hydrazine. Moreover, the prepared flexible catalysts seem to be a promising anode material for DHFCs.
(Invited) Effect of Water Management for Cathode Catalyst Layers Using a Non-Noble Metal Catalyst and a Novel Polymer Electrolyte on Cell Performance Hysteresis in Anion Exchange Membrane Fuel Cells
Authors: Uchida Makoto , Otsuji Kanji , Yokota Naoki , Tryk Donald A. , Kakinuma Katsuyoshi , Miyatake Kenji 
Published: December 2020

In this work, we examined the cell performance of membrane-electrode assemblies (MEAs), for anion exchange membrane fuel cells (AEMFCs), using a non-noble metal catalyst and a novel polymer electrolyte. The chemical structure of quaternized poly(arylene perfluoroalkylene), i.e., QPAF-4 (ion exchange capacity: IEC = 2.1 meq g-1) developed in this laboratory1 is shown in Figure 1. Since this membrane is soluble in methanol, it is also suitable for use as an electrode binder. The non-precious metal catalyst cell was loaded with 0.45 mg cm-2 Fe-N-C catalyst supplied by Pajarito Powder on the cathode and 0.20 mgPt cm-2 platinum catalyst on the anode. An MEA in which platinum was loaded (0.20 mgPt cm-2) on both the anode and cathode was prepared for comparison. Pt loaded on carbon black (Pt/CB, TEC10E50E), supplied from TKK Japan, was used as the platinum electrocatalyst.
Figure 2 shows a comparison of Fe-N-C and Pt/CB for their I-V performances at 60 oC, 100% RH, 0 kPag; anode H2 (100 mL/min); cathode O2 (100 mL/min). The cell using the Fe-N-C catalyst exhibited large hysteresis in the I-V curve, i.e., a large difference in potential between increasing and decreasing current. Figure 3 shows a comparison of Fe-N-C and Pt/CB for their I-V performances at 60 oC, 100% RH, 100 kPag; anode H2 (100 mL/min); cathode O2 (100 mL/min). The hysteresis of the I-V performance for the cell using the Fe-N-C cathode decreased with increasing back pressure. The cell exhibited slightly lower open circuit voltage and similar IV performance compared with those using Pt/CB. At the present stage, the loading amount of Fe-N-C catalyst, ionomer content, and porosity of the catalyst layer have not yet been optimized.
We investigated whether the hysteresis originates from the anode or cathode. Based on the results of various I-V measurements, we conclude that the hysteresis is related to water supplied to the cathode using the Fe-N-C catalyst. Further details will be given in this presentation. We found from these results that the water management is essential, due to its requirement for the cathode reaction, for high-performance AEMFCs. Finally, these results demonstrate the viability of the use of low-cost materials such as non-noble metal catalysts for the AEMFC.
Acknowledgement
This project was partly supported by NEDO Japan through funds for the “Advanced Research Program for Energy and Environmental Technologies” and the Japan Society for the Promotion of Science (JSPS) and the Swiss National Science Foundation (SNSF) under the Joint Research Projects (JRPs) program.
References
1. H. Ono, T. Kimura, A. Takano, K. Asazawa, J. Miyake, J. Inukai, K. Miyatake, J. Mater. Chem. A, 5, 24804 (2017).

Figure 1
Alternative Mechanistic Considerations: Charactering Multiple Reaction Pathways for the Oxygen Evolution Reaction
Authors: Ha Mai-Anh , Alia Shaun M , Larsen Ross E 
Published: December 2020

H2 remains an important chemical precursor in processes such as the Haber-Bosch process to synthesize ammonia and hydrocracking for refining of hydrocarbons and also exists as an alternative fuel for transportation. Currently, 95% of H2 is produced by steam methane reforming, whose byproduct is pollutant CO. Electrolysis is a clean, efficient method run at room temperature to split water into H2and O2. However, electrolysis is not cost-competitive with steam methane reforming, utilizing large amounts of platinum group materials. Computational chemistry can give atomic and electronic levels of understanding of a material by identifying highly active facets of a known material or predicting the catalytic potential of unknown materials. We will model catalysts used in the oxygen evolution reaction, the half-cell reaction requiring the most catalyst and occurring many orders of magnitude slower than the hydrogen evolution reaction. We will focus on the effect of the ensemble: modeling different facets of iridium oxide, characterizing all possible configurations of key reaction intermediates, and incorporating explicit solvation to fully understand the nuances of optimizing a premier catalyst such as IrO2. In particular, we will focus our calculations on two facets: (110), the more thermodynamically stable facet and (001), a potentially more active facet due to the presence of undercoordinated, surface Ir sites. We will compare the reaction profile of the ensemble of key reaction intermediates on the (110) versus the (001) facet and in vacuum versus with solvation. The ensemble of intermediates allows us to explore multiple reaction pathways on the surface that have not been characterized.
Figure 1. A schematic summarizing the different isomers found at each reaction step (TOP) and the reaction profile of the oxygen evolution reaction on the (110) facet of iridium oxide (BOTTOM).

Figure 1
Oxygen Evolution Reaction of NiO Nanowalls with a Three-Dimensional Framework
Authors: Takimoto Daisuke , Hideshima Sho , Sugimoto Wataru 
Published: December 2020

It is important to optimize the mass transport of electrons, ions and gases to enhance the catalytic activity and efficiency for electrolysis. We previously reported that nanosheets possess higher electrocatalytic activity compared to nanoparticles.1 This is attributed to the large electrochemically active surface area of nanosheets. However, nanosheets tend to re-stack, leading to poor mass transport and low efficiency. In this study, we propose a new electrocatalyst with a three-dimensional architecture composed of a framework of NiO nanowalls toward oxygen evolution reaction (OER).
Macro porous carbon (MPC) was purchased from Toyo Tanso (CNovel®, Japan) and used as template. MPC was dispersed in 2-methoxyethanol, and nickel acetylacetonate was dissolved in 2-methoxyethanol. The suspension was mixed for 3 days and collected by centrifugation. The obtained powder (MPC@NiO
x
) was dispersed in 2-methoxyethanol. After solvothermal treatment, the solution was centrifuged, and the dried powder was heated in air to yield macro porous NiO (3D-NiO). NiO particles were prepared without the macro porous carbon template. OER activity of the electrocatalysts was investigated using a three-electrode system consisting of a Pt mesh counter electrode and a Ag/AgCl (sat. KCl) reference electrode. 1.0 M KOH (30°C) was used as the electrolyte.
TEM images of 3D-NiO showed a 3D structure constructed by 2D NiO nanowalls with very thin and smooth surface. The structure of 3D-NiO was replicated from the MPC template; MPC was oxidatively removed by calcination at 400°C. The redox peaks at a half peak potential of E
1/2 = 1.49 V vs. RHE were observed in the cyclic voltammograms for 3D-NiO and NiO particles. These redox peaks were attributed to the transformation of b-Ni(OH)2 and b-NiOOH (Ni(OH)2 « NiOOH + H+ + e-).2 The OER current at 1.8 V vs. RHE of 3D-NiO was 15 times larger than that of NiO particles. The onset potential of the OER for 3D-NiO was similar to that for NiO particles, indicating that the OER mechanism was not sensitive to the morphology of NiO. The result strongly indicates that the 3D structure with 2D nanowall is a superior design for OER electrocatalyst. Considering the diffusion path of evolved O2 molecules, the enhanced activity could also be attributed to the meso pore nature of 3D-NiO.
This work was supported by Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Young Scientist (Grant Number 18K14054).

References

D. Takimoto, K. Fukuda, S. Miyasaka, T. Ishida, Y. Ayato, D. Mochizuki, W. Shimizu and W. Sugimoto, Electrocatalysis, 8, 144 (2017).

M.-S. Kim, T.-S. Hwang and K.-B. Kim, J. Electrochem. Soc., 144, 1537 (1997).
Durability and Performance Limitations in Currently Available Alkaline Exchange Membrane Electrolysis Materials and the Relationship to Total System Cost
Authors: Motz Andrew R , Capuano Christopher , Ayers Katherine E. 
Published: December 2020

Anion exchange membrane (AEM) electrolyzers have the potential to reduce the cost of hydrogen generated via. electrolysis through reducing the cost of stack materials, improved electrochemical kinetics, and exhibiting a higher tolerance range for water purity (e.g. brackish and saltwater electrolysis). These potential benefits have resulted in a large amount of research funding, and as a result several commercial AEMs are now available. Additionally, several commercial, AEM specific catalysts are also available.
With the increasing maturity of AEM electrolysis (still in the very early stages), there is a growing need for benchmark performance and durability using only membrane electrode assembly (MEA) materials that are commercially available. Several materials, both polymers and catalysts, will be discussed for both performance and durability under differential pressure. The incumbent technology, proton exchange electrolyzers, typically operate up to 435 psig differential H2 pressure accomplished through a combination of electrolysis and electrochemical compression. To provide a more direct comparison to the current technology, durability will be measured under differential H2 pressure. Additionally, test will be performed to identify presence of electronic shorting or cross-cell leaks, both cell failures that will result in apparent improved performance due to the lower operating voltage.
For industry to adopt AEMs, there must be demonstrated device reliability and projected system cost savings. A techno-economic analysis will be performed to compare AEM and PEM electrolysis in several different scenarios to better understand the state of the technology.
High-Efficiency Reversible Hydroxide Exchange Membrane Fuel Cells
Authors: Yang Fan , Green Zach , Strasser Derek , Shi Wenjuan , Rojas-Carbonell Santiago , Yan Yushan , Xu Hui 
Published: December 2020

Reversible fuel cells have advantages over rechargeable batteries due to their high energy density, minimal self-discharge, and low cost. Reversible hydroxide exchange membrane fuel cells (HEMFCs) are attractive due to their ability to work with platinum-group-metal (PGM)-free catalysts. HEMFCs and hydroxide exchange membrane electrolyzers (HEMELs) have been separately studied. However, it remains a challenge to integrate the two into a single reversible cell. The major factors that limit the development of unitized reversible HEMFCs are low performance of bifunctional oxygen catalysts, hydroxide membrane stability, hydroxide ion conductivity and water management. Previous research has been focusing on electrolyte-fed HEMELs 1. However, the corrosive alkaline solution presents material compatibility problems and increases the system and balance of plant (BOP) complexity. For example, the presence of alkaline solutions can increase the complexity of the unitized reversible fuel cell system due to adding extra water purging steps during the transition between electrolyzer mode and fuel cell mode.
In this study, we have developed a pure water-fed reversible HEMFC which makes it possible to use stainless steel to replace the titanium current collectors commonly used in proton exchange membrane electrolyzers (PEMELs) to reduce the manufacturing cost. We have made tremendously progress to make the HEMFC reversible without the addition of alkaline or bicarbonate electrolyte. This is the first reported reversible HEMFC with the highest round trip efficiency (RTE) at an appreciable current density (48% @ 0.5 A/cm2). The reversible test result is shown in Figure 1. In addition to the initial RTE evaluation, we also achieved promising MEA stability. However, a voltage increase was also observed in the initial stage of the durability test which is presumptively attributed to the ionomer wash-out and catalyst layer restructuring. These challenges have been addressed by innovative electrode design.

Acknowledgement: The project is finacially supported by the Department of Energy's HFTO under the Grant DE-EE0008438.

Reference:

Abbasi, R., Setzler, B. P., Lin, S., Wang, J., Zhao, Y., Xu, H., Pivovar, B., Tian, B., Chen, X., Wu, G., Yan, Y., A Roadmap to Low‐Cost Hydrogen with Hydroxide Exchange Membrane Electrolyzers. Mater.2019, 31, 1805876

Figure 1
Considering Two-Phase Flow in Three-Dimensional Computational Fluid Dynamics Simulations of Proton Exchange Membrane Water Electrolysis Devices
Authors: Lopata Joseph Steven , Kang Zhenye , Young James L. , Bender Guido , Weidner John W. , Cho Hyun-Seok , Shimpalee Sirivatch 
Published: December 2020

Computational studies are employed to construct our understanding of systems and to reduce the monetary and temporal demands of research and development. Proton exchange membrane water electrolysis (PEMWE) devices, with their intricate two-phase transport phenomena and numerous realizable applications, provide an excellent opportunity to utilize computational fluid dynamics (CFD). Toghyani et al.1 modeled the performance of a high-temperature, vapor-fed PEMWE device using CFD simulations, finding fair agreement with prior experimental studies. For low-temperature electrolysis, Nie and Chen2 used a mixture model to study the flow regimes in liquid-fed channels.
We employed a CFD model to simulate a PEMWE device, exploring the viability of isothermal and non-isothermal mixture models for a liquid-fed cell. The flow rate was altered to study the change in cell temperature and performance, and the model results were compared to experimental data. Additionally, bulk properties of the porous transport layer at the anode were altered to examine performance effects; such effects were expected to be virtually non-existent in light of experimental observations.3,4 The results demonstrate when a continuum assumption is best utilized to predict electrolysis efficiency.
References:

S. Toghyani, E. Afshari, and E. Baniasadi, Journal of Thermal Analysis and Calorimetry, 135, 1911–1919 (2019).

J. Nie and Y. Chen, International Journal of Hydrogen Energy, 35, 3183–3197 (2010).

T. Schuler, T. J. Schmidt, and F. N. Büchi, Journal of The Electrochemical Society, 166, F555–F565 (2019).

J. Lopata et al., Journal of The Electrochemical Society, 167, 064507 (2020).

Figure 1
Active and Stable Bifunctional Oxygen Electrocatalysts and Catalyst Layers for Unitized Regenerative Fuel Cells
Authors: Rhodes Christopher P. , Godinez-Salomon Fernando , Albiter Luis 
Published: December 2020

Proton exchange membrane unitized regenerative fuel cells (PEM-URFCs) that can function in both fuel cell and electrolysis modes provide potential weight and cost advantages over discrete systems; however, improved catalysts and catalyst layers are needed to improve performance and stability. PEM-URFCs require bifunctional oxygen electrocatalysts that facilitate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), and significant challenges remain to increase catalyst activity, reduce precious metal loading, and obtain long-term stability over the wide potential voltage ranges that occur switching between fuel cell and electrolyzer modes. We have recently shown that bimetallic nanoframes, formed from thermal treatment of noble-metal decorated nanosheets, provide bifunctional oxygen electrocatalysts with significantly higher activity compared with monometallic structures, evaluated using a rotating disk electrode configuration.1 The nanostructured bimetallic alloys utilize noble metal-non-noble transition metal interactions to alter the surface electronic structure, and the unsupported nanostructure provides a carbon-free matrix with three-dimensional accessibility to the catalytically active sites. In addition to design of the catalytically active site, the catalyst layer has important influences on mass transfer and flooding within PEM-URFCs. From our preliminary evaluations, the oxygen catalyst nanostructure, catalyst loading, and catalyst layer composition have significant effects on the performance of PEM-URFC membrane electrode assemblies (MEAs) that operate in both fuel cell and electrolyzer modes.

References

Godínez-Salomón, F.; Albiter, L.; Mendoza-Cruz, R.; Rhodes, C.P. Bimetallic Two-dimensional Nanoframes: High Activity Acidic Bifunctional Oxygen Reduction and Evolution Electrocatalysts, ACS Applied Energy Materials
,
2020,
3, 2404-2421. http://dx.doi.org/10.1021/acsaem.9b02051
(Invited) Electrochemical Li Nucleation, Growth, and Dissolution in Oxide Solid Electrolyte Systems
Authors: Motoyama Munekazu , Kitagawa Mizuki , Hirota Masaharu , Yamamoto Takayuki , Iriyama Yasutoshi 
Published: December 2020

A great deal of attention has been paid to all-solid-state-lithium battery, which can theoretically achieve a higher energy density than Li ion batteries. One of the key technologies to achieve a high energy density for all-solid-state-lithium battery is to realize highly reversible Li metal anode free from the short-circuiting of solid-state electrolyte (SE).
Many of oxide SEs such as Li7La3Zr2O12 (LLZ) are mechanically hard materials with shear moduli on the order of 102 GPa. So, it had been believed that an oxide SE could act as a separator to prevent Li dendrite growth from the anode side through the SE. However, short-circuiting events have been found to still occur even with the SE. Figure 1 shows voltage transients during Li plating/stripping cycles at various current densities using Li/Ta-doped LLZ (LLZT)/Li symmetric cells 1. Short-circuiting events occurred in any cells, but it was found that the cycling stability significantly depended on the surface treatment. SiC-polishing removed surface Li2CO3 and LiOH from LLZT samples but simultaneously created thin damage layers on the surface. This damage layer was electrochemically inactive. Hence, LLZT etched in a 1.0 mol dm−3 aqueous solution exihbited the longest cycling stability because damge layers were removed from the surface during the etching.
Many researchers have put a lot of effort into controlling the Li plating/stripping processes in solid-state battery, but there is still a lack of fundamental understanding of electrochemical Li deposition and dissolution in solid-state electrolyte systems. I will present the results of our recent studies on Li plating/stripping reactions at “Li-free” interface as well as Li/SE interface 2,3.

Acknowledgement

This work was in part supported by JSPS KAKENHI Grant Number JP19H05813 (Grant-in-Aid for Scientific Research on Innovative Areas “Interface IONICS”).

References

[1] M. Motoyama et al., “The Active Interface of Ta-Doped Li7La3Zr2O12 for Li Plating/ Stripping Revealed by Acid Aqueous Etching ”, ACS Appl. Energy Mater.,
2, 6720 (2019).
[2] M. Motoyama et al., “Modeling the Nucleation and Growth of Li at Metal Current Collector/LiPON Interfaces”, J. Electrochem. Soc.,
162, A7067 (2015).
[3] M. Motoyama et al., “In Situ Scanning Electron Microscope Observations of Li Plating/Stripping Reactions with Pt Current Collectors on LiPON Electrolyte”, J. Electrochem. Soc.,
165, A1338 (2018).

Fig. 1. (Left) Voltage transients during galvanostatic cycling of Li plating/stripping with various LLZT samples: (top) #3000-polished, (middle) #400-polsihed, (bottom) 5m-HCl-etched. (Right) Optical images of molten Li in contact with LLZT samples prepared by each polishing or etching condition on the left-hand-side figure.

Figure 1
Yttria-Stabilized Zirconia Capping Layer on Pt Cathode By Atomic Layer Deposition
Authors: Yang Byung Chan , Kye Seunghyeon , GO Dohyun , Shin Jeong Woo , Kim Hyong June , Cho Gu Young , An Jihwan 
Published: December 2020

Atomic layer deposition (ALD) has the advantage of being able to deposit various materials as nanometer-scale thin films at low temperatures, and to precisely control thickness and doping levels. Due to these advantages, ALD has been applied in various fields including solid oxide fuel cells (SOFCs). SOFC is an echo-friendly next-generation energy conversion device that has high efficiency and fuel-flexibility. However, due to the high operating temperature (1000 ℃) of conventional SOFCs, problems such as thermal degradation and material selection occur. In order to solve this problem, low temperature SOFCs (LT-SOFCs) that can be operated below 500 ℃ are being studied. However, as the operating temperature decreases, oxygen reduction reaction (ORR) at cathodes of SOFCs also slows down. Therefore, engineering cathode surface, where ORR takes place, is important to improve the performance of LT-SOFCs.
In this study, we deposited an ultra-thin film (~ 5nm) yttria-stabilized zirconia (YSZ) overlayer on the Pt cathode surface of LT-SOFC through ALD. In addition, the effect of doping level on the performance and thermal stability of LT-SOFC was studied by varying the cycle ratio of zirconia and yttria. The doping level of the YSZ overlayer was controlled to be 6, 13, 16 and 23 mol%, which were confirmed through XPS analysis. The performance of the cell with 16 mol% -doped YSZ overlayer at 450 ℃ showed the highest maximum power density, which was 70 % higher than that of cell without the overlayer. In addition, the activation resistance, which is mostly from ORR, was also reduced by 27 %. In addition, in the prolonged operation for 5 hours at 450 ° C, it was found that the performance of the cell without the overlayer was reduced by 80 %, while that of the cell with 16 mol%-doped ALD YSZ overlayer was reduced by 40 %. This result shows that the thermal stability was also improved when the ALD YSZ overlayer was deposited.