bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Highly Acidic Mixed-Metal (W, Zr) Catalytic Matrices for Dispersed Noble Metal Nanoparticles: Electrooxidation of Hydrogen and Small Organic Molecules
Authors: Kulesza Pawel J , Rutkowska Iwona Agnieszka 
Published: February 2020

Application of metal oxides as active matrices in electrocatalysis is particular importance. The hydrous behavior, which favors proton mobility and affects overall reactivity, reflects not only the oxide’s chemical properties but its texture and morphology as well. What is of importance to electrochemical science and technology, certain nonstoichiometric mixed-valence oxides could exhibit pseudo-metallic conductivity and possess appreciable catalytic activity.
Recently, mixed oxide systems stabilized through Zr-O-W bonds have been demonstrated to be very attractive acid catalysts exhibiting high catalytic activities and good stabilities in many demanding industrial reactions. For electrocatalytic applications, mixed-valent tungsten(VI,V) oxide and zirconium(IV) oxide have been sequentially deposited and integrated through voltammetric potential cycling to form sub-microstructured films on glassy carbon electrode. The mixed WO3/ZrO2 systems are characterized by fast charge (electron, proton) propagation during the system’s redox transitions. By dispersing metallic Pt and bimetallic platinum-ruthenium (PtRu) electrocatalytic nanoparticles over such active WO3/ZrO2 supports, the electrocatalytic activities of the respective systems toward the oxidation of hydrogen and small organic molecules (formic acid, methanol, ethanol or dimethyl ether) have been enhanced even at decreased loadings of noble metal nanostructures (for hydrogen oxidation) as well as in terms of both increasing the electrocatalytic currents and lowering the onset potentials of organic fuels’ reactions. The enhancement effects should be attributed to features of the mixed metal oxide support such as porosity and high population of hydroxyl groups (due to presence of ZrO2), high Broensted acidity of sites formed on mixed WO3/ZrO2, fast electron transfers coupled to unimpeded proton displacements (e.g. in HxWO3), as well as strong metal-support interactions between nanosized noble metals (Pt, Pd or PtRu) and metal oxo species. The fact that WO3/ZrO2 nanostructures are in immediate contact with the metallic catalytic sites leads to the competitive interactions (via the surface hydroxyl groups) with undesirable reaction intermediates (including CO adsorbates). Thus their desorption (“third body effect”) or even oxidative removal (e.g. of CO to CO2) are feasible.
Furthermore, during oxidation of ethanol, when rhodium nanoparticles have been dispersed in between WO3 and ZrO2 layers (toward formation of the nanoreactor system), significant electrocatalytic current enhancements are observed. The result can be rationalized in terms of the formation of sub-microstructured nano-reactors in which Rh induces splitting of C-C bonds in C2H5OH molecules toward CHx/CH4 and CO adsorbate species, or even methanol-type intermediates, that could be further electrooxidized at PtRu catalytic centers. Further mechanistic studies along this line are planned.
Graphitic Carbon Nitride-Graphene Hybrid Nanostructure as a Catalyst Support for Polymer Electrolyte Membrane Fuel Cells
Authors: Mansor Noramalina , Jia Jingjing , Miller Tom , Suter Theo , Belen Jorge Ana , Gibbs Christopher , Shearing Paul R. , McMillan Paul F. , Mattevi Cecilia , Shaffer Milo , Brett Daniel J.L. 
Published: February 2020

Graphitic carbon nitride is a new class of semiconducting graphene-like polymeric material with visible light absorption and photocatalytic properties. In addition to high nitrogen content and tunable structure, it was shown that graphitic carbon nitride based on polytrazine imide (PTI) sheets exhibit excellent anti-corrosion ability in ex-situ fuel cell environment.1 However, in bulk form, their low surface area and poor conductivity limits their applications in fuel cells.
In this work, an exfoliation route was established to produce PTI ink containing single to few-layer nanosheets. The ink was then processed to produce 3D networks of carbon nitride nanosheets/reduced graphene oxide (rGO-PTI) hybrid nanostructure with large interconnecting pores for fast mass transport of reactants (Figure 1a) and high surface area. The material was decorated with low loadings of platinum which also acts as spacers to prevent the restacking of the nanosheets, and then investigated for its electrochemical properties and applications as a durable catalyst support for PEM fuel cells. Initial results show that the cathode catalytic activity of Pt/rGO-PTI hybrid is significantly improved in comparison to Pt/PTI or Pt/rGO (Figure 1b), and long-term potential cycling shows that it is more durable than commercial Pt/C. The work is now being extended to develop high-performance and stable membrane electrode assemblies (MEA) for PEM fuel cells.

N. Mansor, A. Belen Jorge, F. Corà, C. Gibbs, R. Jervis, P. F. McMillan, X. Wang, D. J. L. Brett, J. Phys. Chem. C 2014,
118 (13), 6831-6838

Figure 1
The Challenges to Ultra-Low-Platinum PEMFC Cathode and the Electrocatalyst Design Thereof
Authors: Zhang Junliang , Shen Shuiyun , Zhu Fengjuan , Wang Chao , Luo Liuxuan 
Published: February 2020

Polymer electrolyte membrane fuel cell (PEMFC) has been extensively studied because of its many desirable qualities for the automotive application, including high power density, low operating temperature (~80 oC) as well as quick start-up and match-up to the power demand. Although appealing, a challenge caused by the high Pt loading in the cathode should be addressed before the mass production of fuel cell vehicles. In this regard, the research topic is now urgently focused on to use ultra-low Pt loading (≦0.1 gPt/kW) in the cathode of PEMFCs. It is noted that both the electrode kinetics of oxygen reduction reaction (ORR) [1] and mass transport for conventional cathodes with low Pt loading do not apply to the cathodes with ultra-low Pt loading, especially for the local mass transport surrounding Pt particles in the catalyst layer [2]. Herein, the challenges in the ultra-low Pt cathode in terms of ORR kinetics and local transport resistance will be clarified and the corresponding solution in terms of the electrocatalyst design will be provided. How the ORR kinetics on the cathode changes with the Pt loading decreasing will be examined in detail and the difference in the transport resistance in each component (Figure 1), especially the O2local transport between the ultra-low Pt cathode and high Pt cathode will be elucidated. The effects of catalyst type, specific activity, Pt loading as well as the cathode structure on the cell performance will be discussed, thus providing a solid scientific guideline for developing cathodes with ultra-low Pt loading and accelerating the commercialization of PEMFCs using cathodes with ultra-low Pt loading.

Acknowledgements

This work was supported in part by National Natural Science Foundation of China (Grant No. 21373135 and 21533005) and Science Foundation of Ministry of Education of China ( Grant No. 413064).

References

[1] Y. Huang, J.L. Zhang, A. Kongkanand, F.T. Wagner, J.C.M. Li, J. Jorné, Transient platinum oxide formation and oxygen reduction on carbon-supported platinum and platinum-cobalt alloy electrocatalysts, J. Electrochem. Soc., 2014, 161 (1): F10-F15.
[2] Y. Ono, T. Mashio, S. Takaichi, A. Ohma, H. Kanesaka, K. Shinohara, The analysis of performance loss with low platinum loaded cathode catalyst layers, ECS Transactions, 2010, 28 (27) 69-78.

Figure 1
Facile Synthesis of High Performance Platinum-Cerium Oxide Nanocatalysts for Methanol Oxidation
Authors: Valk Peeter , Nerut Jaak , Kanarbik Rait , Lust Enn 
Published: February 2020

Electrooxidation of methanol has been studied intensively in the scientific community, and various catalysts have been developed for direct methanol fuel cells.
In this study, platinum-cerium oxide nanoparticles have been synthesised, exhibiting high activity towards methanol electrooxidation. The materials were electrochemically characterised using rotating disk electrode, cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy methods. Scanning electron microscopy, X-Ray diffraction, inductively coupled plasma mass spectrometry and BET surface area mesurements were performed to characterise the physical properties of the synthesised materials.
The methodology of the synthesis of the materials was straightforward and resource efficient. The synthesised nanocatalysts have a very uniform dispersion on the catalyst support material, and a narrow size distribution.
Even at low platinum loadings, the materials have a lower overpotential towards methanol oxidation than commercial Pt-Vulcan catalysts. Based on cyclic voltammetry measurement data, the peak potential for the synthesised materials was 40 mV more negative than for the commercial material in the anodic potential scan, and 60 mV more negative in the cathodic potential scan.
In addition to the high currents for methanol oxidation, extremely high currents were achieved in the cathodic potential sweep, in the region attributable to the oxidation of carbon monoxide. Methanol and carbon monoxide poisoning of the nanocatalysts was unnoticeable during the experiments.
The results of the study lay a promising foundation for the investigation of nanocatalysts containing other rare earth metal oxides, as well as to the investigation of the electrooxidation of ethanol or other organic fuels on composite catalysts.
Acknowlegements
The authors wish to thank P. Paiste for ICP-MS measurements and J. Aruväli for XRD measurements
This work was supported by the EU through the European Regional Development Fund TK141, the institutional research funding project IUT20-13 of the Estonian Ministry of Education and Research, the Estonian Energy Technology Program Project No. SLOKT10209T, Estonian Materials Technology project 3.2.1101.12-0019, Estonian Center of Excellence in Science Project TK117T, grant ETF9352 and PUT55.
Water Electrolysis Using Water Absorbing Porous Electrolyte Cell
Authors: Terayama Yuki , Haji Takamasa , Mori Kouhei , Matsumoto Hiroshige 
Published: February 2020

We have reported so far water electrolysis by use of a water absorbing porous electrolyte that works under similar conditions to a polymer electrolyte electrolysis cell (PEEC) [1]. This cell consist of a surface-proton conducting metal oxide nanoparticles as proton-conducting electrolyte, a controlled-hydrophobic electrocatalytic layer, and fully hydrophobic gas diffusion layer (GDL) to generate pressurized hydrogen and oxygen gases. In this presentation, we will discuss the optimized preparation condition for membrane electrode assembly (MEA), which consist of electrolyte, electrode, and GDL layers. We also show that the hydrogen gas generation rate depend on the supplied water pressure (ΔP).
MEA of the water electrolysis cell is prepared as follows: The GDL films were formed by compressing of acetylene black/poly(tetrafluoroethylene) (PTFE) (=1/6, weight ratio) composite powder using Newton Press under 6 kN cm-2 for 1 min and successive heat treatment at 360 °C for 15 min. Electrode part with Pt loading of 2.0 mg cm-2 on top of the GDL films was formed using hot-press at 300 °C for 3 min under 300 kgf cm-2, which is consisted of consisted of platinum carbon (Pt/C) / PTFE / titanium phosphate ionomer composite. Finally, electrolyte layer on top of electrode layer was prepared by coating of titanium sulfonate/Nafion (=9/1, weight ratio) slurry and hot-pressing at 140 °C under 100 kgf cm-2 for 1 min. The fabricated MEAs were different sizes with diameters of 30 mm and 12 mm for anode and cathode sides, respectively. The current-voltage characteristic and generation hydrogen gas is measured by putting the fabricated MEA into the cell as shown Figure 1. The distilled water is supplied from cathode side and is pressurized using nitrogen gas in the ΔP range from 0 MPa to 0.25 MPa. The gas evolution rates of hydrogen during water electrolysis were evaluated by gas chromatography to be determined by 1% hydrogen/argon calibration curve.
The gas evolution rate of hydrogen increased with increasing ΔP from 0 MPa to 0.10 MPa, and reaches a maximum value at 0.15 MPa. At ΔP higher than 0.15 MPa, the rates decreased to almost the same value at 0 MPa. We supposed that the generated gas was leaked to outside of the cell in lower pressure region than 0.15 MPa. On the other hand, in higher region than 0.15 MPa, the generated gas in the water phase by water electrolysis was not completely separated to gas phase.
The obtained evolution rate was compatible with the theoretical value calculated by Faraday’s law. However, electrolysis voltages were high compared with conventional PEEC. Possible reason is inhomogeneous state of electrode layer and electrolyte layer with lower electrical conductivity.

Acknowledgements

This work was supported by CREST in JST.

References

(1) S.-J. Kim, T. Sakai, H. Oda, J.-I Hamagami, Y. Okuyama, M. Matsuka, S. Ohta, Y. Shimizu, T. Ishihara, H. Matsumoto Electrochem.
2012
80(4), 246.

Figure 1
Innovative Approach on Nano-Structuring of Electrode for Solid Oxide Cells
Authors: Myung Jaeha , Neagu Dragos , Irvine John T. S. 
Published: February 2020

Solid oxide cells (SOCs) are electrochemical systems capable of operating reversibly and therefore may serve as versatile energy converters. Electrolysis mode, electricity can be converted to fuels or other valuable chemicals, on the other hand, fuel cell mode converts efficiently fuel to electricity on demand. Due to their severe operating conditions, the ideal fuel electrode materials has not been found yet to accomplish of its requirements such as electronic and ionic conductivity, and catalytic activity with strong stability in redox condition, while several high performance air electrode materials -have been identified. For a long time, Ni-YSZ cermet has been regarded as the embodiment of this functional trinity. However, even though degradation associated with reversible operation can be mitigated, the cermet electrodes still suffered from agglomeration during redox condition. Recent electrode designs have been developed to microstructures consisting of a porous mixed ionic electronic conductor backbone decorated with metallic nanoparticles (typically Ni) by impregnation method. However, these are still hindered by the lack of cost and time-effective methods to produce both robustness and high-performance from their nanostructured electrodes. Here, a simpler alternative, will be introduced, exsolution whereby the catalytically active metal is substituted in the crystal lattice of the backbone in oxidizing conditions and exsolved on the surface as designed metal particles under reduction condition. Here we demonstrated a simple and highly effective in situ method for producing nanostructured electrodes capable of delivering high performances in both fuel cell and electrolysis mode. Both the nanostructures and corresponding electrochemical activity show no degradation over 150 hours of testing.
Enhancement of Thermal Stability of Sputtered Nanoporous Pt Thin Film Using Oxygen Plasma Treatment in Low Temperature Solid Oxide Fuel Cells
Authors: Liu Kang-Yu , Su Pei-Chen 
Published: February 2020

Sputtered nanoporous platinum (Pt) thin films are common choices as catalytic cathodes for low temperature (300~500°C) solid oxide fuel cells (LT-SOFCs) for its high catalytic activity towards oxygen reduction reaction. However, the nanoporous pure Pt is vulnerable to thermal coagulation during high temperature operation, which often causes irreversible deterioration to the cell performance. In our earlier work, physical confinement of the nanoporous Pt with a few nanometers of zirconia (ZrO2) conformal coating by atomic layer deposition (ALD) improved the thermal stability of Pt significantly, with more than 50% of the cell power density retained after 80 hours of operation. Still, around 29.5% of cell power density degradation was observed in cells using ALD-ZrO2 capped nanoporous Pt cathode. It is likely that the poor adhesion between the Pt cathode and the yttria-stabilized zirconia (YSZ) electrolyte that caused the triple phase boundaries to be unstable under high temperature operation and therefore a significant thermal degradation is still observed.
In this work, we studied the effect of adhesion between Pt and YSZ on the morphological stability of nanoporous Pt at the Pt/YSZ interface. The surface of YSZ electrolyte was treated with oxygen plasma to modify the wettability between ALD-ZrO2 capped Pt and YSZ. The contact angle of a water droplet on the untreated YSZ surface was 80˚, while it dropped to 16˚ on the oxygen-plasma treated YSZ surface, meaning a more hydrophilic YSZ surface was obtained. The oxygen-based functional groups may have formed after the oxygen plasma treatment and increased the YSZ-water interfacial energy. The additional chemical bonding may exist if the nanoporous Pt films are deposited on surface-treated YSZ to stabilize the morphology of nanoporous Pt at the Pt/YSZ interface. The surface confined nanoporous Pt thin film cathodes were annealed at 600°C to induce the agglomeration, followed by delamination of the Pt cathode film from the YSZ substrate using double cantilever beam (DCB), in order to investigate the morphological stability of the nanoporous Pt at the Pt/YSZ interface after oxygen plasma treatment. The interfacial morphology observation showed that the Pt agglomeration at the Pt/YSZ interface remained significantly severe for Pt cathode with only ALD-ZrO2 surface capping. For Pt cathode deposited on YSZ substrate treated with 5 minutes of oxygen plasma at 18 watts showed improved interfacial thermal stability. A fuel cell with ALD-ZrO2 capped nanoporous Pt cathode thin film deposited on the oxygen-plasma treated YSZ electrolyte was tested. It was observed that the performance degradation was effectively hindered by the oxygen plasma treatment after 75 hours of operation at 450°C.

Figure 1
Secondary Phases at Cathode/Electrolyte Interfaces
Authors: Szász Julian , Wankmüller Florian , Joos Jochen , Wilde Virginia , Störmer Heike , Gerthsen Dagmar , Ivers-Tiffée Ellen 
Published: February 2020

Understanding the nature of a cathode/electrolyte interface in solid oxide fuel cells (SOFC) is still a challenge, especially if this interface is composed of a mixed conducting cathode, i.e., La1-xSrxCo1-yFeyO3-
δ (LSCF), and a bilayer electrolyte, i.e., Gd-doped Ceria (GDC) interlayer and Y2O3 stabilized ZrO2 (YSZ) electrolyte. The interface resistance can vary over more than two orders of magnitude [1], resulting from variable volume and local distribution of the poorly ionic conducting secondary phase SrZrO3(SZO) [2] and GDC-YSZ interdiffusion (ID) [3].
This contribution will introduce a COMSOL Multiphysicsmodel, which simulates the performance characteristics of such heterogeneous cathode/electrolyte interfaces. The model is based on 3D-reconstruction data of an interface region, which was characterized (i) electrically by in-situ electrochemical impedance spectroscopy and (ii) by ex-situ elemental analysis using TEM/EDXS. Our model calculations quantify the contributions of both secondary phases, SZO and ID to the cathodic polarization resistance, but also a contribution of ID to the ohmic resistance, corresponding well to the performance measurements. Our results further reveal that interface morphology, i.e. volume and local distribution of secondary phases, plays a significant role. When GDC is sintered at high temperatures (see Fig.1 at 1300°C) to a continuous and dense ID layer (green color), SZO formation is still significant (turquoise color), but a comparatively small area of “free” pathways for oxygen ions from LSCF→GDC→ID→YSZ can reduce the polarization resistance up to two orders of magnitude. On the contrary; when GDC is sintered at lower temperatures, a much thicker and continuous SZO layer blocks the diffusion of oxygen ions, corresponding to the highest polarization resistance.
From our investigation we conclude that because secondary phases are inherently present and their local contribution overshadows every high-performing material property, it is of particular interest to deepen the understanding of functional cathode/electrolyte interfaces by using high-resolution analysis techniques.

References

[1] J. Szász, F. Wankmüller, V. Wilde, H. Störmer, D. Gerthsen, N. H. Menzler, E. Ivers-Tiffée, ECS Transactions, 66 (2) (2015) 79-87.
[2] H. Yokokawa, N. Sakai, T. Horita, K. Yamaji, M.E. Brito, H. Kishimoto, J. Alloys Compd., 452 (2008) 41-47.
[3] A. Tsoga, A. Naoumidis, A. Gupta, D. Stöver, Mater. Sci. Forum, 308-311 (1999) 794-799.

Figure 1
Design and Fabrication of a Flat Tubular SOFC Stack
Authors: Xie Bin , Ji Weijie , Ming Li , Jiang Yousong 
Published: February 2020

SOFC is now considered to be a most promising power generating technique for its high energy conversion efficiency and no pollution. To accelerate the commercial application of SOFcs, flat tubular stacks combining tubular and planar cell structures, show high performance and low cost fabrication techniques. To reduce the cost, metallic materials are applied as interconnects and supports and Ag-Cu braze is applied as ceramic-metallic seal.
In this work, we design and fabricate a 600W anode supported flat tubular SOFC stack. The stack is composed of 36 replaceable flat tubular cassettes made by FeCrAl alloy. Cells composed of NiO-YSZ (anode)/ YSZ (electrolyte)/LSM-YSZ (cathode) are sealed on cassettes by Ag-Cu braze.
Effect of the WO3/Lipon Solid Electrolyte Interface on the Performance of All Thin Film Inorganic Electrochromic Devices
Authors: Oukassi Sami , Poncet Séverine , Giroud-Garampon Cédric , Salot Raphaël 
Published: February 2020

In this work we report on the realization of an all solid state thin film electrochromic device and the effect of WO3/LiPON (lithium phosphorus oxynitride) interface on the cycling performance.
An icon-type device representing a 1 cm² QR code design was fabricated on glass substrate with the following architecture: ITO/WO3/LiPON/LixV2O5/AZO-Ag-AZO (Fig.1). Cross-sectional FIB-SEM observation showed layers with uniform thicknesses and interfaces free of delamination, voids or interdiffusion defects. The lithium in-depth distribution measured by ToF-SIMS showed a uniform and almost constant profile at the insertion electrodes (Fig.2)
The device bleaching and coloring was observed upon +/-2V voltage application with switching time of 60 s. Constant voltage bleaching/coloration cycles have been carried out, the icon type devices exhibited a moderate capacity fading during the first 1000 cycles with an average loss of 0.01% per cycle followed by an almost stable capacity up to 3000 cycles (Fig.3).
Furthermore, electrochemical impedance spectroscopy (EIS) carried out at different state of charges on ITO/WO3/LiPON/Li cell revealed the existence of an important charge transfer resistance at the WO3/LiPON interface (Fig.3). After comparison with EIS data obtained from the full electrochromic device, the charge transfer resistance at WO3/LiPON interface was identified as the predominant limiting step for fast switching times of considered devices.

Figure 1