bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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) 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
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.
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.
Scale up of Proton-Conducting Ceramics into Multi-Cell Stacks
Authors: Le Long Quoc , Hernandez Carolina Herradon , O'Hayre Ryan , Sullivan Neal P 
Published: December 2020

Proton-conducting ceramics are emerging as an enabling material for efficient electricity generation, energy storage, and fuels synthesis. While recent advancements at the lab-scale are highly encouraging, there are few reports of scaling cell size beyond the button cell, and no demonstrations of multi-cell stacks. Through support from the U.S. Department of Energy, researchers at the Colorado School of Mines are scaling up protonic-ceramic devices from the button-cell level into small, multi-cell stacks as illustrated in the figure. Both fuel-cell and electrolyzer stacks are in development. The order-of-magnitude increases in the physical size of the delicate membrane-electrode assembly (MEA) bring concerns regarding mechanical strength and robustness. The compatibility of protonic-ceramic materials with stack-packaging materials – metallic interconnects, current collectors, glass-ceramic sealants, and gaskets – has witnessed limited study. In this presentation, we describe selection and tuning of materials, fabrication procedures, and operating conditions to achieve reasonable performance and low degradation in protonic-ceramic fuel cells (PCFCs) stacks.
We find highest stack electrochemical performance and durability when utilizing electrolytes based on BaCe0.4Zr0.4Y0.1Yb0.1O3-d (BCZYYb). The anode support is a nickel-electrolyte composite, while the cathode is BaCe0.4Fe0.4Zr0.1Y0.1O3-d (BCFZY). The planar MEAs reach 5 cm2 in active area. The circular stack design enables a measure of flexibility in MEA physical size and shape, and provides balance in stress distribution from thermal- and chemical-expansion. The MEAs are packaged within ferritic-steel interconnects and macor frames to form multi-cell stacks. Our three-cell stack demonstrates encouraging performance, reaching 0.69 and 0.47 W cm-2 under H2 and CH4 fuels, respectively, at 600 ºC. A cathode-electrolyte interlayer of 10%-gadolinium-doped ceria proves critical in achieving stack degradation as low as 1.5% kh-1.

Figure 1
Photo-Enhanced Grain Boundary Ionic Conductivity in Gadolinium Doped Ceria
Authors: Klotz Dino , Defferriere Thomas , Gonzalez-Rosillo Juan Carlos , Rupp Jennifer L.M. , Tuller Harry L. 
Published: December 2020

Oxide-based ionic and mixed ionic-electronic conductors (MIEC) play strategic roles in applications ranging from energy conversion and storage to thin film nano-ionic devices such as fuel cells, batteries, permeation membranes and nano-electronic memory and sensing devices. Most cost-effective production methods for fabricating both bulk and thin films samples generally result in the formation of polycrystalline microstructures with grain boundaries, where the crystallographic periodicity is interrupted.
Grain boundaries possess significantly different properties compared to the bulk and often block ion migration. Due to the high resistance and large activation energies, they represent a ubiquitous problem to overcome for a variety of electrochemical energy storage and conversion devices especially for low temperature applications. Space-charge potential barriers, featuring depletion zones and band bending, forming at the interface between adjacent grains, have been used to explain their blocking nature in polycrystalline semiconductors.
In the field of photoelectrochemistry, above band-gap light is well-known to contribute to reduce band bending at interfaces by providing additional charge carriers to screen potential barriers. Here, we show that the same principle can be applied to ionic conductors as well, and that we can significantly decrease the grain boundary impedance contribution in such systems.
We illustrate photo-enhanced ionic conduction in a thin film of 3% Gd-doped ceria upon illumination by UV light, whose photon energy is slightly above ceria’s band-gap. In fact, we demonstrate the ability to decrease the grain boundary resistance by 72% at 250°C and reduce its activation energy nearly in half from 1.12 eV in the dark to 0.68 eV under UV light illumination. We further demonstrate that this effect is not caused by heat, electronic conductivity, surface catalysis or other effects. Our findings are based on electrochemical impedance spectroscopy (EIS) and intensity-modulated photocurrent spectroscopy (IMPS) measurements, performed on polycrystalline and epitaxial samples, and backed by theoretical considerations of grain boundary potential height and space charge regions.
This work was supported by JSPS Core-to-Core Program, A. Advanced Research Networks: “Solid Oxide Interfaces for Faster Ion Transport”, Department of Energy, Basic Energy Sciences and the Swiss National Science Foundation.

Figure 1