bluuebunny/crossref_metadata_2025 huggingface dataset:
Clarification of Active Sites for Oxygen Reduction Reaction on Silver and Nitrogen Co-Doped Carbon Materials
Authors: Kruusenberg Ivar , Kuzmin Anton , Shainyan Bagrat A. , Hu Jin-Song , Macdonald Digby D.
Published: December 2020

The oxygen reduction reaction (ORR) is one of the most important reactions in both fuel cells and metal-air batteries [1]. ORR needs catalysis to lower the electrochemical overpotential for high-voltage output for these technologies and, so far, platinum (Pt) has been the main catalyst of choice. However, as the expensive, traditional Pt/C catalysts are not viable in the long term, much effort has been focused on heteroatom doped and non-precious metal catalysts [2]. Metal-nitrogen co-doped carbon materials have emerged as the main candidates for replacing the platinum-based catalysts. Among these materials, silver and nitrogen co-doped catalysts have proven to exhibit high electrocatalytic activity for the ORR in alkaline media. However, no clear understanding exists about the exact catalytic mechanism and rational design of these catalysts.

In this work, we synthesized model catalyst of silver and nitrogen co-doped carbon (Ag-N-C) by using simple precursors. Silver phthalocyanine and multi-walled carbon nanotubes have been used for the one-pot synthesis of Ag-N-C material. The morphology of the catalyst was studied by the transmission electron microscopy and the surface elemental composition was examined with X-ray photoelectron spectroscopy (XPS). The catalysts‘ activity towards ORR in 0.1 M KOH is assessed using the rotating disk electrode (RDE) method and the results are compared to those of commercial Pt/C catalysts (Figure 1). The created Ag-N-C model catalyst reveal a highly enhanced activity via the synergistic, doubly beneficial effects of the support material and formed catalytic centers, which were studied by density functional theory (DFT). Our theoretical calculations, which matched with the experimental findings, provide necessary hints on ORR mechanistic issues on the developed Ag-N-C model catalyst and will guide how to design and prepare better active non-Pt catalyst materials for fuel cell and metal-air battery electrodes, as well as providing deeper insight into the ORR mechanism occurring on this type of catalysts.

References

[1] M. Shao, Q. Chang, J.P. Dodelet, R. Chenitz, Recent Advances in Electrocatalysts for Oxygen Reduction Reaction, Chem. Rev. 116 (2016) 3594-3657.

[2] K.M. Villemson, K. Kaare, R. Raudsepp, T. Käämbre, K. Šmits, P. Wang, A.V. Kuzmin, A. Šutka, B.A. Shainyan, I. Kruusenberg. J. Phys. Chem. C 123 (2019) 16065-16074.

Figure 1
Template Synthesis of Ag@Fe-N-Doped Carbon Electrocatalyst for Oxygen Reduction Reaction in Alkaline Media
Authors: Gong Chong , Wang Zhihuan , Chen Xing , Chen Yingjie , Yu Liyan , Dong Lifeng
Published: December 2020

With the development of fuel cells, it is critical to find suitable oxygen reduction reaction (ORR) catalyst materials to replace current commercial Pt/C catalysts. On the one hand, atomically dispersed Fe-N-C with highly active Fe-Nx centers has been proved to be one of the best ORR catalysts comparable to the Pt/C. In addition, structural effects and strong metal-carrier interactions greatly improve performance. Therefore, various templates have been used for controlling the structure of Fe-N-C catalysts. For instance, polypyrrole is widely utilized as a nitrogen-rich carbon precursor, and hollow porous Fe3O4 microspheres with polypyrrole (PPy) encapsulated on the surface were pyrolyzed to obtain Fe-N-doped double-shell hollow carbon microspheres. Also, silica balls were applied as templates to fabricate hollow Fe-N-C carbon using a nano-casting method. These hollow structural Fe-N-C materials showed efficient ORR catalytic activities. On the other hand, Ag-based catalysts are also considered as possible candidates for ORR in alkaline medium due to their comparatively low cost and good CO tolerance capability. For example, Janus nanostructured Ag@N-C synthesized by pyrolyzing core-shell Ag@PPy demonstrated comparable ORR activity to the Pt/C, which was largely attributed to the synergistic effect between Ag nanoparticles and carbonized PPy shell. Therefore, rational design of porous Fe-N-C structure with Ag nanoparticles would achieve excellent ORR electrocatalysts.

Herein, Ag@Fe3O4 nanoparticles were synthesized by a solvothermal method and utilized as templates, and PPy enveloped on the template surface functioned as nitrogen and carbon sources. After pyrolysis, hollow porous Fe-N-C was decorated with Ag nanoparticles, which demonstrated excellent ORR catalytic activity and durability in alkaline medium. Therefore, this study provides a new simple method for preparing Ag@Fe-N-C hybrid catalysts.
Fabrication of Iron Phosphide Nanoparticle/Carbon Paper Electrodes Via Electrophoretic Deposition for HER Catalysis
Authors: Park Yoonsu , Kang Hyeri , Hong Yun-kun , Ha Don-Hyung
Published: December 2020

As a renewable energy source to replace traditional fossil fuels, hydrogen is a promising sustainable energy carrier due to its eco-friendly nature and high energy density. Although Pt-based materials are widely used as catalysts for generating hydrogen through water electrolysis because of their high catalytic activity, Pt is expensive, and its scarcity hinders the commercialization of large-scale hydrogen production. The development of alternative low-cost materials with low hydrogen evolution reaction (HER) overpotential is the key to achieve low price and highly efficient hydrogen generators such as proton-exchange membrane water electrolysis (PEMWE). Among the numerous candidates of earth-abundant materials, transition metal-based phosphides (TMPs) are suitable for HER applications due to their low toxicity, high electrical conductivity, and catalytic activity. Especially, FeP is in the spotlight as a HER catalyst due to its high catalytic activity in solutions with a wide pH range, and this is a competitive material for large-scale commercial production of hydrogen, since Fe is one of the most abundant elements on earth.

In this study, we synthesized the colloidal FeP nanoparticles (NPs) via a hot injection process, so that the pre-synthesized Fe NPs can be converted to FeP NPs through the phosphorization reactions by various phosphorus sources (trioctylphosphine, triphenylphosphite (TPP), tris(diethylamino)phosphine, and tri-n-butylphosphine). Different HER activities were induced by the phase transformation of NPs over the controlled reaction time for the NP samples synthesized with each phosphorus precursor. The FeP synthesized using TPP achieved excellent HER activity with an overpotential of 76 mV at 10 mA cm-2 in 0.5 M H2SO4 as measured by drop casting the catalyst on Ti foil. In terms of the fabrication for the efficient HER electrode, the prepared FeP NPs were deposited on the carbon paper (CP) via electrophoretic deposition (EPD), which is a suitable method for the fabrication of NP films that can be used for various electronic applications. Different morphologies and catalytic activities of the FeP/CP samples were derived by controlling EPD parameters such as mixing ratio of solvents, NP concentration, and deposition voltage. The optimized EPD process lead to excellent HER activity of the FeP/CP with an overpotential of 38 mV and 91 mV at 10 mA cm-2 in 0.5 M H2SO4 and 1 M KOH, respectively. The maximum activity of the catalyst was mainly attributed to the large active surface area and low charge transfer resistance due to the strong contact between the NPs and CP. A PEMWE single cell with the FeP/CP cathode achieved 1.2 A cm-2 at cell voltage of 2.0 V. This study of the EPD procedure for fabricating the NP film from the colloidal NP catalysts contributes to advance manufacturing of HER electrodes for efficient hydrogen generation through water electrolysis.
New Synthesis Strategies for Transition-Metal Phosphide Based Water Splitting Electrocatalysts
Authors: Das Debanjan , Nanda Karuna Kar
Published: December 2020

Transition metal phosphides (TMPs) have emerged as an intriguing class of efficient electrocatalyst finding widespread application in hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Currently adopted wet chemistry and solid-gas synthesis techniques rely on the use of surfactants/ toxic organic solvents or toxic gas which restricts facile fabrication of TMPs. Moreover, hybridizing TMPs with suitable carbon support (graphene, carbon nanotubes etc.) favorably optimizes the electrochemical activity of TMPs. However, this is often achieved via post-synthesis modification further complicating the synthesis procedure.

In an attempt to overcome these limitations, we have recently developed a solid state, phosphine free method to fabricate Co2P nanoparticles encapsulated N, P co-doped CNTs. These as prepared catalysts were applied as a bi-functional electrocatalyst for HER and OER. In order to increase the surface area and loading of Co2P nanoparticles, we next designed Co2P encapsulated CNTs grafted N, P co-doped hollow spheres via MOF-templated strategy with superior catalytic activity compared to Co2P@CNTs.[1] [2]

We then introduced sub-2nm IrP2 nanoparticles encapsulated bilayer N, P co-doped graphene as a novel electrocatalyst which exhibits better HER activity than benchmark Pt/C in acid, neutral as well as the alkaline medium. Interestingly, careful tuning of the reaction parameters also enables the synthesis of phase pure Ir2P.

In conclusion, the versatile strategy developed here can be extended to fabricate a variety of TMPs with widely varied applications.

[1] D. Das and K.K. Nanda, Nano Energy, 2017, 30, 303-311

[2] D. Das, A.Das, M.Reghunath and K.K Nanda, Green Chemistry, 2017,19, 1327-1335
Effect of Ionomer Binders on Performance and Durability of Catalyst Layers in Polymer Electrolyte Electrolyzers
Authors: Park Jong-Hyeok , Kim Beom-Suk , Park Jin Soo
Published: December 2020

Hydrogen based energy conversion devices such as water electrolyzers or fuel cells require catalyst layers as electrode providing the simultaneous movement of gas, liquid, and electron. The movement of ions generated and consumed at two electrodes, i.e., anode and cathode, respectively, takes place by ionomer binders made of perfluorosulfonic acids. Ions should be transported inside electrodes to participate in anodic and cathodic reactions. Ion pathway is normally in liquid electrolyte. Regardless, the introduction of any aqueous phase in energy conversion devices causes many problems during fabrication, operation, maintenance, and so on. In addition, if gas penetration or gas evolution is one of phenomena taking place at electrodes, the electrodes should be porous. Thus, much efforts have been devoted to develop quasi-solid electrolytes such as gel polymer, ion exchangeable polymers, impregnation of ions in porous matrix and so on. Among the candidates, ion exchangeable polymers are quite often chosen as ion conducting media for energy conversion devices. The technique to introduce ion exchangeable polymers within electrodes for oxidation and reduction reactions is to solidify catalyst inks consisting of electrocatalyst, dispersion of ion exchangeable polymers, controlling solvents and additives by evaporation of all solvents in catalyst inks. Ion exchangeable polymers could be dispersed in various solvents. It causes different shapes of ion exchangeable polymers in solvents, for instance, cylindrical rods, a less-defined large particles, coils and so on. Such different types of ion exchangeable polymers form distinguished structure catalyst layers. In this study, the effect of solvents dispersing ion exchangeable polymers on the performance and durability of catalyst layers was investigated. Electrochemical characterization such as I-V polarization, cyclic voltammetry, impedance and so on and microscopic characterization such as SEM and TEM were carried out to evaluate the performance and durability of catalyst layers.

Acknowledgment

This research was supported by the Hydrogen Energy Innovation Technology Development Program of the National Research Foundation (NRF) funded by the Ministry of Science, ICT ＆ Future Planning(NRF-2019M3E6A1063677).
Impact of Membrane and Gas Diffusion Layer on AEM Electrolyzer Performance
Authors: Lindquist Grace , Oener Sebastian , Xu Qiucheng , Motz Andrew R , Keane Alex , Capuano Christopher , Ayers Katherine E. , Boettcher Shannon W.
Published: December 2020

Electrochemical water splitting enables the use of renewable energy to produce O2 and H2 gas, vital for many energy and industrial applications. The leading commercial systems are based on liquid-alkaline and proton-exchange-membrane (PEM) technology. Liquid-alkaline systems operate at large-scale using inexpensive catalyst materials but use caustic electrolyte and cannot operate under the high differential pressures required for compressed H2 output. PEM systems use a solid-polymer electrolyte to allow for high-differential-pressure operation with pure water but require expensive precious-metal catalysts and corrosion-resistant cell materials. Anion-exchange membrane (AEM) electrolyzers, a promising new technology, combine the benefits of liquid alkaline and PEM systems. However, the technology is premature and needs further development. AEMs are prone to performance losses such as membrane degradation and instability, limited OH- conductivity, and membrane dehydration due to water transportation limitations. This behavior can vary based on membrane structure. Understanding the fundamental processes that lead to these performance losses is essential for AEM development. I will discuss the influences of membrane, ionomer, and gas-diffusion layer (GDL) material interactions on AEM electrolyzer performance as well as the importance of cathode water flow during AEM operation (Fig. 1a). To study these parameters, the performance of five different AEM materials with various gas diffusion layer (GDL) supports were evaluated. Interfacial contact between the membrane and GDL has a more-significant impact on performance than bulk membrane conductivity. Directly coating the catalyst material on the membrane improves interfacial contact between the membrane and GDL, which decreases ionic transport losses (Fig. 1b) Applying the knowledge gained, we demonstrate AEM electrolyzer operation at <2.3 V at 1 A cm-2 in pure water (Fig. 1) using only commercially available materials. Understanding AEM material interactions contributes to both a fundamental understanding of ionic transport in membrane electrolysis and to improving electrolyzer technology. This knowledge will improve AEM materials design and performance, thus facilitating the expansion of global electrolyzer capacity to help meet future renewable hydrogen demands.

Figure 1
(Invited) High Efficiency PEM Water Electrolysis Enabled By Advanced Catalysts, Membranes and Processes
Authors: Capuano Christopher , Ayers Kathy , Manco Judith , Wiles Luke , Errico Shaina , Zenyuk Iryna V. , Weber Adam Z. , Kusoglu Ahmet , Danilovic Nemanja , Ulsh Michael , Mauger Scott A , Pfeilsticker Jason , Alia Shaun M
Published: December 2020

Commercial water electrolysis technologies, including proton exchange membrane electrolysis (PEMWE), are the only renewable hydrogen generation technologies that can achieve the U.S. Department of Energy (DOE) cost targets within the next ten years at the required scale, based on the supply chain maturity and materials performance. In particular, membrane and electrode modifications have enabled the use of advanced electrolysis membranes to achieve the efficiency targets, while nanoengineered alloy catalyst layers (CLs) have been pursued to meet the cost and efficiency targets. These advancements have been achieved by building the basic understanding to allow the successful technical development and include: (1) Mechanical and chemical understanding of membranes in liquid water below 90oC; (2) Characterization of as-deposited electrodes and MEAs after operation; (3) Water management in the anode catalyst layer, dependence on catalyst loading and porous transport layer form factor; and (4) Long-term degradation rate and stability of engineered alloy Ru-Ir alloy nanocatalysts in well-defined anode catalyst layers.

Nel Hydrogen’s pathway to meet these DOE goals is through the i) use of 50-75% thinner membranes that operate at 80-90 oC, while controlling mechanical creep and gas crossover; ii) reducing the catalyst loading to 1/10th the current value on both electrodes, while controlling water distribution and the porous transport layer/catalyst layer (PTL/CL) electrochemical interface; iii) incorporation of a less stable but more active Ru containing catalyst managed on the anode side of the cell, which is achievable with lower voltage operation (accomplished via low ohmic drop in the anode catalyst layer, thinner membranes, and higher temperature operation); and iv) fabricating a membrane electrode assembly (MEA) integrating all of these characteristics.

In this talk, some of the advancements achieved and how these have impacted the cost of hydrogen will be discussed, as well as the longer-term targets that need to be reached to provide the robustness required for commercial applications. Additionally, cost models will be compared along with sensitivity analysis to show how the impact of operating parameters, with regard to the capital and operational expense for the PEM electrolysis technology cost, show the critical areas to focus on to provide the largest impact towards meeting cost target goals and what is required to go beyond.

Figure 1
Investigating the Interface of TiOx/PGM Coating of Porous Transport Layers Used in PEM Electrolyzers By Surface Analysis
Authors: Liu Chang , Shviro Meital , Zaccarine Sarah F , Gago Aldo Saul , Gazdzicki Pawel , Morawietz Tobias , Biswas Indro , Schierholz Roland , Pylypenko Svitlana , Lehnert Werner , Carmo Marcelo
Published: December 2020

Titanium porous transport layer (PTL) situating at the anode side of a PEM electrolyzer is subjected to harsh oxidizing conditions such as high anode overpotential, low pH, and oxygen evolution [1, 2]. Under these conditions, titanium (Ti0) changes its oxidation state over time, which induces the formation of a thin but continuously growing layer of passivated titanium (TiOx). Consequently, the electrical conductivity of the titanium fibers is adversely affected, fatally decreasing cell performance and durability [3, 4].

Here, we demonstrate a scalable and simple approach to using iridium or platinum as a protective layer for titanium-based PTLs. In this work, 4000 hour stable durability profiles are achieved when PTLs are coated with only 0.1 mg·cm-2 platinum or iridium (10 times reduction of Au or Pt typically used in current commercial electrolyzers). The real morphology of the TiOx/PGM (platinum group metal) coating interface of PTL is shown by different surface analysis methods. We found that the thickness of TiOx layer of iridium coated PTL did not further increase after the long-term operation. The results of this work show how the interface of a well-protected titanium fiber behaves against passivation after a long-term operation under real electrolysis conditions.

Reference

[1] M. Carmo, D.L. Fritz, J. Merge, and D. Stolten, A comprehensive review on PEM water electrolysis. International Journal of Hydrogen Energy, 2013. 38(12): p. 4901-4934.

[2] K. Ayers, N. Danilovic, R. Ouimet, M. Carmo, B. Pivovar, and M. Bornstein, Perspectives on Low-Temperature Electrolysis and Potential for Renewable Hydrogen at Scale, in Annual Review of Chemical and Biomolecular Engineering, Vol 10, J.M. Prausnitz, Editor. 2019, Annual Reviews: Palo Alto. p. 219-239.

[3] C. Rakousky, U. Reimer, K. Wippermann, M. Carmo, W. Lueke, and D. Stolten, An analysis of degradation phenomena in polymer electrolyte membrane water electrolysis. Journal of Power Sources, 2016. 326: p. 120-128.

[4] C. Liu, M. Carmo, G. Bender, A. Everwand, T. Lickert, J.L. Young, T. Smolinka, D. Stolten, and W. Lehnert, Performance enhancement of PEM electrolyzers through iridium-coated titanium porous transport layers. Electrochemistry Communications, 2018. 97: p. 96-99.
Separation of Polarizations Using Shifted Electrode Arrangement in Proton Exchange Membrane Water Electrolysis
Authors: Watanabe Konosuke , Araki Takuto , Nagasawa Kensaku , Kuroda Yoshiyuki , Mitsushima Shigenori
Published: December 2020

Proton exchange membrane water electrolysis (PEMWE) has attracted much attention because of its advantages such as the ability to downsize the equipment and produce high-purity hydrogen. For further improvement of the efficiency and durability of PEMWE, it is necessary to separate and examine polarizations. However, it is difficult to separate the anodic and cathodic polarizations by the AC impedance method. Also, it is difficult to separate resistance polarizations by using the reference poles with normal electrodes as shown in Figure 1 (a). Therefore, we are developing a device in which the electrode arrangement of both poles is deliberately shifted and a reference electrode is placed on each of the anode and cathode, as shown in Figure 1 (a) [1]. Since the phenomena in PEMWE are complicated due to the mutual influence of material/electric charge transport and reaction distribution, a multiphysical numerical analysis considering the potential distribution in the shifted electrode structure have been performed using COMSOL Multiphysics 5.4. Ohm's law was solved for the ionic charge transport in the electrolyte and the ionomer of the catalyst layer and also applied to the contact resistance between the electrode and the current collector. Butler-Volmer's equation was used for the activation overpotential at both poles. Figure 1(b) shows the electrolyte potential distribution when the electrode arrangement is shifted, and the potential distribution was completely changed from the (a). Figure 2 shows the relationship between the shift amount of electrode and the potential difference between both reference electrodes. The potential difference between both reference electrodes increases as the shift amount of electrode increases, and the rate of change of the potential difference decreases as the shift amount increases. Design and data processing based on these numerical results will lead to the development of devices that can perform more accurate separation of polarizations.

Reference

1) S. Mitsushima, H. Kashiwagi, K.Nagasawa, and Y. Kuroda, ECS Meet. Abstr., MA2019-02, 1715 (2019).

Figure 1
Carbon Nanotube-Based Pmg-Free Electrocatalysts with High Oer and ORR Activities
Authors: Nakashima Naotoshi
Published: December 2020

The development of a PGM-free electrochemical catalyst with high electrochemical activity and durability is a strong demand from industry. We have reported the design, fabrication and characterization of nanocarbon (especially multi-walled carbon nanotubes)-based electrocatalysts with high performance[1-6]. In this meeting, we will report our recent studies on the design, fabrication, nanostructures and catalytic activities of nanohybrids of nanocarbons with i) Ni/Fe spinel oxides, ii) Ni/Fe layered double hydroxide, and iii) Ni/Fe/sulfide. We have found that these catalysts show high OER and ORR catalytic activities.

References

[1] N. Nakashima (Editor), “Nanocarbons for Energy Conversion-Supramolecular Approach”, Springer, 2018, pp. 1-564.

[2] J. Yang, P. Ganesan, A. Ishihara, N. Nakashima , ChemCatChem (invited review), 2019, 11, 5929-5944.

[3] J. Yang, J. Tao, T. Isomura, H. Yanagi, I. Moriguchi, N. Nakashima, Carbon, 2019, 145, 565-571.

[4] J. Yang, F. Toshimitsu, T. Fujigaya, N. Nakashima, J. Mater. Chem. A, 2017, 5, 1184-1191

[5] J. Yang, T. Fujigaya, N. Nakashima, Sci. Rep., 2017, 7, art.no.45384.

[6] J. Yang, J. Cheng, J. Tao, M. Higashi, M. Yamauchi, N. Nakashima, ACS Appl. Nano Mater.
2019, 2, 6360-6367.
Towards Fast and Accurate Online Optimization of SOFC through the Hybrid Simulation Method
Authors: Xu Haoran
Published: December 2020

Solid oxide fuel cells (SOFC) are promising devices in converting fuels directly into electricity. The utilisation of hydrocarbons and biomass in the SOFC is especially attractive for their widely distribution, cheap price and high energy density in volume. The long-term operation of SOFC using these fuels remains difficult due to the lack of effective control system, which not only requires a precise analysis but also a fast response. Here, we investigate a hybrid model for the on-line analysis of SOFC. The model combines multi-physics simulation (MPS) and artificial intelligent (AI), which overcomes the complex of MPS for model-based control system and saves cost of building the database (compared with experiments) for AI training. The maximum temperature gradient and heat generation are the two target parameters analysed for the safe and efficient operation of the SOFC. The results show a precise prediction is achieved from the trained AI algorithm, where the relative error between MPS and AI models are smaller than 1%. This method can also serve as an effective tool for the prediction and optimisation of other non-liner, dynamic systems.
A Phase Field Study on the Microstructure Evolution in the Ni-YSZ Electrode of SOC Under Operating Condition: Comparison between Ni(OH)2 Diffusion and Ni-YSZ Wettability Change
Authors: Lei Yinkai , Cheng Tian-Le , Abernathy Harry , Kalapos Thomas , Hackett Gregory A , Wen You-Hai
Published: December 2020

A phase field model is developed to simulate the microstructure evolution in the Ni-YSZ electrode of solid oxide cell under operating conditions. Both the mechanisms of Ni(OH)2 diffusion and Ni-YSZ wettability change have been incorporated into the model and linked to the operating conditions. The effect of the operating condition on the microstructure evolution has been investigated under both the fuel cell and electrolysis mode. The effects of these two mechanisms on the microstructure evolution at different operating conditions have been analyzed and compared.
Experimental and Numerical Analyses of Mass Transfer in Solid Oxide Cells
Authors: Nakajima Hironori
Published: December 2020

In solid oxide cells including solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs), spatial reactant/product concentration variations cause current and temperature distributions over the electrodes. Design optimization of the cell geometry and gas flow configurations, which include the design of separator (interconnector) ribs and flow channels for a planar cell, improves the efficiency and chemical/thermo-mechanical durabilities of practical stacks. Numerical models validated by in-situ measured current distributions are powerful tool for such optimization. In the present study, current and hydrogen partial pressure distributions have been modeled for a tubular SOFC [1] and planar SOFCs [2] using finite element modeling (COMSOL Multiphysics) on the basis of theoretical consideration of the concentration overpotential and the Nernst loss from local exchange current density determined by local reactant/product concentrations [3, 4] so that the models agree with in-situ measurements using segmented cathodes [5-7], determining the exchange current densities, electrode porosities, electrolyte ion conductivities, and electrode ion/electron conductivities. Anode-supported honeycomb SOFCs [8] and cathode-supported honeycomb SOECs [9] were also modeled for three-dimensional gas transports in agreement with their experimental current-voltage characteristics.

[1] Ö. Aydın and H. Nakajima, Journal of the Electrochemical Society, 165 (5), F365-F374 (2018).

[2] Ö. Aydın, T. Ochiai, H. Nakajima, T. Kitahara, K. Ito, Y. Ogura, and J. Shimano, International Journal of Hydrogen Energy, 43 (36), 17420-17430 (2018).

[3] H. Nakajima and T. Kitahara, Marine Engineering, 53(2), 230-236 (2018).

[4] H. Nakajima, ECSarXiv, in press.

[5] Ö. Aydın, T. Koshiyama, H. Nakajima, and T. Kitahara, Journal of Power Sources, 279, 218-223 (2015).

[6] T. Ochiai, H. Nakajima, T. Karimata, T. Kitahara, K. Ito, and Y. Ogura, ECS Transactions, 78, 1, 2203-2209 (2017).

[7] H. Nakajima, T. Kitahara, and E. Tsuda, ECS Transactions, 78 (1), 2109-2113 (2017).

[8] H. Nakajima, S. Murakami, S. Ikeda, and T. Kitahara, Heat and Mass Transfer, 54 (8), 2545-2550 (2018).

[9] Y. Iwanaga, H. Nakajima, and K. Ito, ECS Transactions, 91 (1), 2707-2712 (2019).
The Sabatier Electrolyzer: Harnessing Proton-Conducting Ceramics to Upgrade Carbon Dioxide into Methane
Authors: Pan Zehua , Duan Chuancheng , Le Long Quoc , El Hageali Sami , Zhu Liangzhu , Hernandez Carolina Herradon , O'Hayre Ryan , Sullivan Neal P
Published: December 2020

We present our development of the Sabatier Electrolyzer to synthesize CH4 and O2 from CO2 and H2O feed streams. Our work seeks to integrate steam electrolysis and hydrogen production with carbon dioxide hydrogenation into a single Sabatier Electrolyzer reactor based on proton-conducting ceramic membranes and Sabatier catalysts. When powered by solar- and / or wind-energy, the Sabatier Electrolyzer has the potential to store intermittent renewable electricity in the form of commodity chemicals while simultaneously reducing carbon dioxide emissions, thereby addressing two principle societal concerns in a single device.

The Sabatier Electrolyzer concept is illustrated in the figure. H2O and CO2 are fed to steam and fuel electrodes, respectively, of a protonic-ceramic electrolysis cell. An external power source drives H2O splitting at the steam electrode. The product O2 is exhausted from the cell. The product protons are driven across the protonic-ceramic membrane to the fuel electrode, where they react with CO2 to form CH4 and H2O. The combination of processes can match the exothermicity of CO2 hydrogenation with the endothermicity of H2O electrolysis to facilitate thermal balance and high efficiency.

Proton-conducting ceramic membranes transport reasonable rates of H+ ions at 400 - 500 ºC with low overpotentials for H2O splitting. This lower operating temperature is reasonably well matched with the CO2-methanation reaction that thermodynamically favors lower-temperatures. The Ni-based catalyst is active for both H2 evolution from the protonic-ceramic material and catalytic methanation of CO/CO2, further promoting the technological combination. Integration of the methanation reactor with the electrolyzer simplifies the system, improves reliability, and provides increased performance within a smaller package than more-prevalent two-stage systems.

We have pioneered a larger-area (active area is 5 cm2) Sabatier Electrolyzer cell composed of a BaCe0.4Zr0.4Y0.1Yb0.1O3-δ (BCZYYb4411) electrolyte, a Ni-BCZYYb4411 fuel electrode support, and a BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) steam electrode. The Ni-cermet fuel electrode serves as the CO2-upgrading catalyst. To date, we have demonstrated CO2 conversion and CH4 selectivity at 55% and 63%, respectively, at 450 °C. This result represents the highest reported electrochemical conversion of CO2 and H2O into CH4 in a single device. In this presentation, we will review our efforts in Sabatier Electrolyzer development, targeting the thermodynamically predicted CO2 conversion and CH4 selectivity of 70% and 95%, respectively.

Figure 1
(Invited) Highlights from Haldor Topsøe - DTU Collaboration on Solid Oxide Based Systems
Authors: Hansen John Bøgild
Published: December 2020

Haldor Topsøe A/S and DTU Energy Conversion (previously Risø National Laboratory) has for more than three decades collaborated on development of Solid Oxide Cell based systems. Professor Mogens Mogensen has been a key person in this collaboration and highlights will be provided from some of these efforts:

Sulfur poisoning of SOFC and SOEC stacks

Development and demonstration of multi kW SOFC systems based on methane, landfill gas, methanol and ammonia

Biogas upgrading by SOEC and methanation
(Invited) Equivalent Circuit Analysis of Mass Transport of Proton- Oxide Ion- Electron Mixed Conductors for Fuel Cells and Electrolysis Cells
Authors: Yashiro Keiji , Okuyama Kotaro , Kawada Tatsuya
Published: December 2020

Recently proton conducting ceramics have been intensively developed for proton ceramic cells (PCCs) for fuel cell and electrolyzer. There are potentially three conduction carriers (proton, oxide-ion, electron hole) in a proton conducting electrolyte, whose partial conductivities vary drastically with change in chemical potential and temperature. Therefore the complicated mass transport phenomena in proton conducting electrolyte must be fully understood to develop the fuel cell and electrolysis cell. While a couple of papers have reported the analysis results of behavior of proton, oxide-ion, and electron hole in the electrolyte [1, 2], the cell behavior including electrode materials are not yet fully understood. In this paper, we analyze complex impedance response of PCCs under the operation conditions of fuel cell and electrolysis cell by equivalent circuit analysis using universal circuit simulator.

[1] H. Zhu, R. J. Kee, Int. J. Hydrogen Energy, 41 (2016) 2931.

[2] D. Poetzsch, R. Merkle, J. Maier, Adv. Func. Mater., 25 (2015) 1542.
(Invited) Controlling the Size and Dispersion of Exsolved Catalyst Particles By Electrochemistry and By Strain
Authors: Yildiz Bilge , Dimitrakopoulos Georgios , Wang Jiayue , Fan Weiwei , Kyriakou Vasileios , Li Ju , Ghoniem Ahmed F.
Published: December 2020

Increasing the performance of Solid Oxide Electrolysis Cells (SOECs) for the production of hydrogen (H2) from water (H2O) splitting requires the use of cathodes with low polarization resistance. In-situ growth of metal catalysts from perovskite oxides (termed catalyst exsolution) has been proposed as a means to decorate the porous electrode with highly dispersed, nanometer-sized catalytic particles [1-3]. These particles are highly active towards reactions of interest and show increased resistance to agglomeration due to their socketed nature [4].

In this work, we investigate the in-situ, on demand exsolution of catalysts by using fuel and electrochemistry as a means to decrease the temperature and duration required to grow catalytic particles on the surface of electrodes. We study the performance, stability, particle morphology and distribution as a function of electrochemical polarization applied at the electrode. Substantial improvement of reaction kinetics is found, consistent with previous reports [5]. In addition, we probe the effect of electrochemical and temperature conditions on the particle size, shape and distribution. In addition, we propose tuning the reducibility of parent oxides to be a good strategy in controlling the size and dispersion of the exsolved particles, and demonstrate this approach on epitaxial perovskite thin films. Moreover, our observations suggest oxygen vacancies to be the potential nucleation sites of the exsolved particles.

The present study provides a new direction towards the generation of nanoparticle-size catalysts on the surface of perovskite oxides given the increasing demand for active and durable catalysts in the field of solid oxide cells and in other energy and fuels conversion processes.

References:

[1] G. Tsekouras et. al. Energy Environ. Sci., 2013, 6, 256–266

[2] Y. Sun et. al. J. Mater. Chem. A, 2015, 3, 11048–11056

[3] G. Dimitrakopoulos et. al. Sustainable Energy & Fuels 2019, 3, 2347-2355

[4] D. Neagu et. al. Nature Communications 8:1855 (2017)

[5] J. Myung et. al. Nature 537 (2016) 528-531
Energy to Molecules and Materials (E2M2): Intermediate Temperature Electrosynthesis of Intermediates, Fuels and Chemicals Using Protonic Ceramic Electrochemical Cells (PCECs)
Authors: Ding Dong , Wu Wei , Ding Hanping , Wang Lucun , Hua Bin , Li Meng
Published: December 2020

Energy and chemical industry showed increasing interest in energy to molecules and materials (E2M2) due to the widely available distributed feedstock and energy input (renewable and/or nuclear energy associated electricity and excess heat). These factors offer new opportunities to those technologies with smaller scale, modularized/distributed, and driven by an integrated system of renewable and other energy sources that can show promise for increased productivity with decreased energy, capital, and operating costs. Intermediate temperature electrosynthesis through solid oxide cells is a promising strategy because of the following advatanges: (1) it can control the product selectivity by changing the operating potentials and temperatures, (2) it can be operated at ambient pressure, (3) it has high production rate and low overpotential, and (4) it can be easily integrated with power and heat from nuclear energy and renewables. Despite of these promising features, this technology still faces many challenges that include but not limited to immature process, relatively low catalyst activity, and unproven operation durability. At Idaho National Laboratory, we have made significant achievements on electrosynthesis of intermediates, fuels and chemicals using natural gas, steam, carbon dioxide and nitrogen through protonic ceramic membrane reactors. The research outcomes have the potential to establish a globally competitive U.S. industry for converting the Nation’s abundant supply of feedstock into conversion-ready intermediates and/or high demand fuels and chemicals.
Mixed-Conducting Composite Materials for High-Temperature Fuel Cells Applications
Authors: Fung Kuan-Zong , Tang Jhih-Yu , Tsai Shu-Yi , Chang Ting-You
Published: December 2020

Mixed ionic/electronic conduction in many electrochemical devices have received great attention. For instance, oxygen transport membrane (OTM) based on (Ba,Sr)(Co,Fe)O3 perovskite exhibit unique hole/oxygen ion mixed conduction behavior for oxygen separation application. Moreover, composite electrodes/electrolytes consisting of electronic and/or multiple ionic conductors have received great attention for high temperature fuel cell application. For example, enhanced conduction was observed when the oxygen ion conductor, doped ceria was directly mixed with Li/K carbonates. The electrical conduction of composite electrolyte was contributed by the migration of oxygen ions in solid state and carbonate ions in liquid state. It was observed that the two-phase electrolytes exhibit coionic (O=/H+) conductors during fuel cell operation under the H2/ air atmosphere. It is believed that highly mobile ions at the interface between doped ceria and carbonates may contribute to the high conductivity of the composite electrolyte. In other words, the super-ionic phase might exist at the interface between doped

ceria and carbonates, where the defect concentrations are high. Similarly, mixed conducting electrodes based on composite electrode (e.g. LSM/SDC, LSM/YSZ) also show improved SOFC performance in comparison to conventional electrode. However, to optimize the mixed conduction, the materials/microstructure designs play an important role. Thus, the objective of this work is to conduct (1) fabrication/design of MIEC and composites (2) microstructure development, (3) characterization of conduction/interfacial kinetics for electrodes/electrolytes in high-temperature fuel cells. High-resolution SEM, XRD, and Electrochemical Impedance Spectroscopy are employed to conduct microstructural, structural and impedance analyses. The electrical conduction behavior of composite electrode/electrolytes will be rationalized based on the pore size, pore distribution and interface area.
Correlation between Fabrication and Operation Conditions for Ce1-XZrxO2-σ (x~0.2) Stability
Authors: Gyu CHOI , Jo Jun-Yeong , Lee Jong-Ho , Kim Yeong-Cheol
Published: December 2020

CeO2 shows high oxygen storage capacity (OSC) by changing the valency of Ce depending on oxygen partial pressures. The addition of Zr into CeO2 (CZO) improves OSC further and has been used in three-way catalysts (TWCs). Recently, researchers applied CZO as an anode in solid oxide fuel cells (SOFCs). Because the operating temperature of SOFCs (~1000K) is higher than that of TWCs (~600K), the thermal stability of CZO becomes an issue. When CZO is fabricated in oxidizing condition, the distribution of metal atoms in CZO would be less stable under reducing operation condition. In this study, we studied the structural stability of CZO as a function of oxygen partial pressure for fabrication and operation conditions; the oxygen partial pressure was varied by changing the number of oxygen vacancies in the model structures. To find energetically favorable structures efficiently among the huge number of possible structures, we used genetic algorithm and lattice statics.
Accelerated Exploration of Stability between Layered and Complex Structures in PrBa1-XSrxCo2-YFeyO5.5
Authors: Kim Yeong-Cheol , Jo Jun-Yeong , Gyu CHOI
Published: December 2020

Layered perovskite structures show high performance as an air electrode in solid oxide fuel cells and proton ceramic fuel cells. Radii difference among metal elements at site A of ABO3 is a prerequisite for conversion of perovskite structures from complex to layered. In this study, we study energetically favorable structures according to change in composition of site A (Pr, Ba, Sr) and site B elements (Co, Fe). 25 compositions were determined by changing x and y in PrBa1-xSrxCo2-yFeyO5.5 (x = 0, 0.25, 0.5, 0.75, 1, and y = 0, 0.5, 1, 1.5, 2). The 2×2×2 supercells with these compositions were studied using DFT. Since the number of possible atomic arrangements for each composition is very large, however, a genetic algorithm was used to search energetically favorable structure efficiently. The highest energy difference between complex and layered structures among the 25 compositions was obtained at x=0 and y=1.
Summary of Various R&D Efforts and Technologies Being Pursued at Nexceris, LLC
Authors: Dogdibegovic Emir , Lockhart Cody , Cooley Nathan , Corwin Chris , Swartz Scott , Seabaugh Matthew Mark , Kidner Neil J.
Published: December 2020

This poster provides an overview or various R&D topics and technologies currently being pursued at Nexceris. The Nexceris’ proved process includes a close collaboration with customers through LEVER Process (Learn, Estimate, Validate, Enhance, Report) which utilizes customer’s technology and Nexceris’ extensive expertise to promote faster product commercialization. Current technologies include development of solid oxide cell (both fuel cells and electolyzers) materials and components, metal supported cells and development of modular stack platforms that can accommodate commercial-size cells. Nexceris is actively involved in development of coatings for bipolar plates and sealing solutions for all cell and stack platforms. The fuelcellmaterials division continues to supply customers with world-class powders, inks, cells, materials and equipment. Other technologies and commercial products currently being pursued at Nexceris include hydrogen detection systems (NTM Sensors and Li-Ion Tamer) which offer a complete solution and alarm systems for stationary applications and monitoring solutions for Li-ion batteries.
Feasibility Synthesis and Characterisation of Gadolinia Doped Ceria Coatings Obtained By Cathodic Arc Evaporation
Authors: Briois Pascal , Ringuedé Armelle , Cassir Michel , Billard Alain
Published: December 2020

The SOFC/SOEC community is now convinced that it is necessary to reduce the operating temperature of fuel cells to make the systems more robust, more reliable and thus to consider large-scale development. At the material level, the change of the reference electrolyte (YSZ) by a cerium compounds allows a significant performance gain for lower temperatures of use. It is obviously necessary to keep in mind the constraints related to the electrolyte application in solid electrolyte device, namely: good ionic conductivity unlike the electrical conductivity which must be low, electrochemical compatibility with the electrodes, be dense and covering on porous substrates.

In this study, Gadolinia doped ceria coatings were deposited by cathodic arc evaporation from a metallic Ce-Gd (90/10 at%) target inserted into a conventional multiarc Ti evaporation target in the presence of a reactive argon-oxygen gas mixture. The structural and chemical features of these films were determined by X-ray diffraction and scanning electron microscopy. Their electrical properties were characterised using impedance spectroscopy measurements. It is shown that the as-deposited coatings crystallise in the fluorite type fcc structure of ceria and that their composition is the same than that of the target. The morphology of the coatings is influenced by the evaporation parameter (stress and droplet). The electrical measurements showed two contributions in Nyquist representation (figure1) and the activation energy is slightly higher than that given in the literature data for the bulk material.

Figure 1 : Nyquist impedance plots of GDC coating, registered at 400°C, for two a.c. signal amplitudes. Logarithms of frequencies are indicated in the figure.

Figure 1
(Invited) Incorporation of Bulk Proton Carriers in Manganese Perovskites Triggered By Charge Disproportionation between Metal and Oxygen Atoms
Authors: Aoki Yoshitaka , Wang Ning , Hinokuma Satoshi , Habazaki Hiroki
Published: December 2020

Protonic ceramic cells (PCCs), including fuel cells and electrolysis cells, are based on protonic conducting Ba(Zr, Ce)O3 electrolytes, and have more advantages at operating temperatures below 600 °C than solid oxide cells (SOCs) based on a oxide ion conducting Y-ZrO2 because the activation energy required for proton conduction (0.3–0.6 eV) is lower than that required for oxide ion conduction (0.8 eV), which is key to lowering fuel cell costs and extending lifetimes. One major issue of protonic cells is a lack of suitable air electrodes that promote the association of protons and oxide ions via oxygen evolution reaction (OER) / oxygen reduction reaction (ORR). Cobaltite-based cathodes, such as (Sm,Sr)CoO3, (Ba, Sr)(Co,Fe)O3, and (La,Sr)(Co,Fe)O3 are typical oxide ion conductors; there is a mismatch of main ionic carriers between the air electrodes and the electrolyte, which limits the efficient area for air electrodes’ reaction to the electrode–electrolyte–gas triple phase boundaries (TPB). Therefore, it is urgent task to develop electrode materials that exhibit H+/e-/O2- triple conduction to extend the efficient reaction zones beyond the TPB and thus reduce the air electrodes’ overpotentials and improve electrochemical performances for PCCs. The transition metal oxides which is capable of hydration at relatively high temperatures must be promising candidate. Nevertheless, robust design concepts for MPECs, namely, transition metal oxides realizing enhanced bulk hydration ability at intermediate temperatures are still missing. Therefore, it is of both fundamental and technological importance to come up with a key ‘descriptor’ to enhance the proton uptakes of electron-conducting metal oxides. Although La1-x
Sr
x
MnO3 (LSM) is a well-known cathode material for SOFCs and recognized as a good oxide ion electron mixed conductor at elevated temperature, it has not been subject to a proton conducting material.

Herein, we report pronounced hydration ability of cubic perovskite type La0.7Sr0.3MnO3-
δ in air conditions attributed to the association of water and oxygen vacancies mediated by Mn oxidation, and subsequent proton attachment to oxygen neighbors in exchange for oxygen hole carriers [1,2]. Hence La0.7Sr0.3MnO3-
δ is capable of up-taking bulk proton carriers in wet air with the proton contents equaling to that of well-known protonic electrolyte material Ba(Zr,Y)O3 at the intermediate temperature (IT) region.

References

[1] N. Wang et al., Incorporation of bulk proton carriers in
cubic-type
La0.7Sr0.3MnO3-δ driven by interplays of oxygen and manganese redox, Chem. Mater. 2019, 31, 8383.

[2] N. Wang et al., Mixed Proton–electron–oxide Ion Triple Conducting Manganite as Efficient Cobalt-free Cathode for Protonic Ceramic Fuel Cells, J. Mater. Chem. A 2020, https://doi.org/10.1039/D0TA03899G.