bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fuel Cell Durability Study of PGM-Free ORR Catalysts
Authors: Chung Hoon T , Zhang Hanguang , Park Jaehyung , Cullen David A. , More Karren L. , Myers Deborah J. , Alp Esen E. , Zelenay Piotr 
Published: May 2020

The focus of LANL’s platinum group metal (PGM)-free catalyst program has been on the improvement and implementation of high-performing and durable cathode catalysts for polymer electrolyte fuel cells (PEFCs). Over the last decade, fuel cell performance of PGM-free catalysts gauged by the current density at 0.9 V
iR-free
in H2-O2 at 1.0 bar has been increased as much as three times (from 12 to 36 mA/cm2). While in durability aspect not much of progress as well as understanding has been achieved.
Fuel cell durability of the catalysts is critical in particular for practical application of the catalysts. Recently ElectroCAT, US DOE supported PGM-free catalyst consortium, proposed the durability test protocol (draft) for PGM-free catalysts. In this presentation, we will report catalyst durability tested following the ElectroCAT-proposed protocol for several catalysts. In conjunction with characterization tools such as cyclic voltammetry, impedance measurement, STEM, x-ray absorption spectroscopy (XAS), and Mössbauer spectroscopy, we will discuss the possible degradation mechanisms as well as pathways to improve the durability of PGM-free catalysts.

Acknowledgements

This research has been supported by DOE Fuel Cell Technologies Office through Electrocatalysis Consortium (ElectroCat). Microscopy was performed as part of a user project supported by Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences, a DOE Office of Science User Facility.
Performance of Sulfonated Phenylated Polyphenylene Membrane As a Polymer Electrolyte Membrane for Water Electrolysis
Authors: Mutambanengwe Rutendo Leah , Peppley Brant A 
Published: May 2020

Traditionally perfluorosulfonic acid (PFSA) membranes such as Nafion are used as membranes for polymer electrolyte membrane water electrolysis (PEMWE) due to their excellent chemical stability, good mechanical strength and high ionic conductivity [1], and low hydrogen permeation. The issue of hydrogen crossover, especially at low current densities or high operating pressures is still of concern since it represents product loss and reduced efficiency. Sulfonated phenylated polyphenylene (sPPP) membranes have been found to be promising electrolyte membranes for electrochemical applications. These sPPPs display significantly less gas crossover compared to Nafion. In addition, they also have high proton conductivity, and are resilient to free radical attack [2]. These properties make them particularly attractive for use in water electrolysis. Tantalum carbide supported iridium based catalysts (IrOx/TaC) have been shown to be potential candidates for use as oxygen evolution reaction (OER) catalysts for water electrolysis [3]. In this study, the use of IrOx/TaC catalyst used in conjunction with sulfonated phenylated polyphenylene membranes as alternative materials for PEMWE to achieve improved performance (utilization and reduced gas crossover) and reduce material costs was investigated. The IrOx/TaC was synthesized in-house using a surfactant mediated method. At low loading, the IrOx/TaC has shown performance comparable to state-of-the-art catalysts. Electrolyser membrane electrode assemblies (MEA)s were fabricated using sPPP membranes, IrOx/TaC (anode) and carbon supported platinum (Pt/C) catalyst (cathode). The electrochemical performance of the MEAs was tested in a single cell electrolyser equipped with an in-situ reference electrode. Current-voltage (I-V) curves were obtained potentiostatically at 80 °C. The I-V performance curves obtained were compared with Nafion based MEAs fabricated using the same IrOx/TaC catalyst. The conductivity of the MEAs was also determined. Scanning electron microscopy (SEM) was used to analyze the morphology and elemental distribution of the electrode surfaces and the cross-section of the MEAs.
References
[1] A. Nikiforov, E. Christensen, I. Petrushina, J. Oluf, and N. J., “Advanced Construction Materials for High Temperature Steam PEM Electrolysers,” in Electrolysis, InTech, 2012, pp. 61–86.
[2] M. Adamski, T. J. G. Skalski, B. Britton, T. J. Peckham, L. Metzler, and S. Holdcroft, “Highly Stable, Low Gas Crossover, Proton-Conducting Phenylated Polyphenylenes,” Angew. Chemie Int. Ed., vol. 56, no. 31, pp. 9058–9061, Jul. 2017.
[3] F. Karimi and B. A. Peppley, “Metal Carbide and Oxide Supports for Iridium-Based Oxygen Evolution Reaction Electrocatalysts for Polymer-Electrolyte-Membrane Water Electrolysis,” Electrochim. Acta, vol. 246, pp. 654–670, Aug. 2017.
Improving Stability and Kinetics of Alkaline HOR Catalysts – Towards Reduced System Cost
Authors: Speck Florian Dominik , Paul Michael T. Y. , Ali S. M. Farhan , Singh Ramesh-Kumar , Böhm Thomas , Kasian Olga , Dekel Dario R. , Kallio Tanja , Cherevko Serhiy 
Published: May 2020

Anion exchange membrane fuel cells (AEMFCs) show great promise in overcoming high cost of currently state of the art proton exchange membrane fuel cells, that rely on expensive Pt catalysts for both the hydrogen oxidation reaction (HOR) as well as the oxygen reduction reaction (ORR). With recent advancements in demonstrating high ORR activity and stability of Fe-N-C catalysts in alkaline environments,1 the HOR suddenly became the bottleneck reaction towards high power density platinum group metal (PGM) -low or -free AEMFCs. While application of PGM-free ORR catalysts is an eventual goal, current state of the art NiM nanoparticles show relatively poor performance in terms of both activity and irreversible oxidation and dissolution.2 Hence, at least for some time, one will need to rely on PGM catalysts for alkaline HOR, where the biggest challenge will be lowering the loading and meanwhile increasing the stability in an alkaline environment. To this end, fundamental understanding of surface processes is required.
In this work we investigate model CeOx covered Pt and Pd electrocatalysts as benchmark materials for the HOR reaction3
,
4. To prepare such model electrodes, we use physical vapor deposition for the formation of PGM and atomic layer deposition subsequently, to yield CeOx surface layers of variable thickness. Activity and stability of the CeOx@Pt and CeOx@Pd electrodes are studied in common rotating disk electrode and on-line inductively coupled plasma mass spectrometry setups, respectively. External analytics, e.g. X-ray photoelectron spectroscopy, are used to further characterize the electrodes before and after degradation studies. We show that stability of the electrodes at the higher anodic potentials can be greatly improved by tuning the thickness of the CeOx layer. Interestingly, this can be achieved without sacrificing and even with a significant enhancement in the HOR activity. This unique performance is explained by assuming that the deposited CeOx films form an ion selective semipermeable passivation layer on the surface of Pd and Pt. We anticipate that, as a next logical step, such layers can be used to stabilize PGM-free Ni alloys and reach the goal of having completely PGM-free AEMFCs.

References

1. P. G. Santori, F. D. Speck, J. Li, A. Zitolo, Q. Y. Jia, S. Mukerjee, S. Cherevko and F. Jaouen, J. Electrochem. Soc., 166, F3311 (2019).
2. E. S. Davydova, F. D. Speck, M. T. Y. Paul, D. R. Dekel and S. Cherevko, ACS Catalysis, 6837 (2019).
3. N. M. Markovića, S. T. Sarraf, H. A. Gasteiger and P. N. Ross, J. Chem. Soc., Faraday Trans., 92, 3719 (1996).
4. H. A. Miller, F. Vizza, M. Marelli, A. Zadick, L. Dubau, M. Chatenet, S. Geiger, S. Cherevko, H. Doan, R. K. Pavlicek, S. Mukerjee and D. R. Dekel, Nano Energy, 33, 293 (2017).
Site-Specific Activity of Pt Single Crystal Surfaces for Oxygen Reduction Reaction
Authors: Liu Guangdong , Zeng Zhenhua , Deng Huiqiu , Steinbach Andrew J. , Greeley Jeffrey 
Published: May 2020

Development of industrial electrocatalysts with improved performance strongly relies on the fundamental understanding of the model systems. Pt(111) surface is probably the simplest, the most fundamental and thus also the most classic model systems for studying the hydrogen and oxygen electrocatalysis, among others. While the wide terrace has long been taken for granted to be the playground of the electrocatalytic reactions, here we demonstrate that such a hypothesis is far incomplete. By combining DFT calculations with experimental measurements, we unravel a 1-2 nm zone with 50% to 5000% activity enhancement for oxygen reduction reaction, which are induced by intrinsic strain that is generated because of the release of surface stress. We further demonstrate how this mechanistic understanding can be utilized to improve the activity of both model electrocatalysts and industrial electrocatalysts.
References
1. Wang, Z. Zeng, W. Gao, T. Maxson, D. Raciti, M. Giroux, X. Pan, C. Wang, J. Greeley,. Science
363, 870-874 (2019).
2. Zeng, J. Greeley, Nano Energy 29 (2016) 369.
Optimization of Platinum Catalyst Electrode with Different Supporting Electrolytes By a Pulse Electrodeposition Technique
Authors: Wu Wei-Sheng , Yeh Tsung-Kuang , Wang Mei-Ya 
Published: May 2020

Due to the low operation temperature and quick start-up, proton exchange membrane fuel cells (PEMFCs) have been investigated nowadays. To improve the power density and short lifetime, much attention has been focused on the catalyst fabrication technique to attain high catalytic activity. Electrodeposition is widely applied using different electrochemical techniques.
With a three-electrode electrochemical cell, Pt catalysts were directly electrodeposited onto the gas diffusion layer. The electrodeposition electrolyte was the hexachloroplatinic acid (H2PtCl6), supporting electrolyte (e.g. Boric acid, perchloric acid or sulfuric acid, etc.) and dispersant (e.g. Ethylene Glycol). The fabrication process of electrodeposited Pt catalyst was conducted under at a specific reduction potential and oxidation potential. By changing the supporting electrolyte, dispersant and applied potentials in fabrication process, the catalytic efficiency of the Pt catalyst electrode was improved.
The Pt dendritic nanostructure was manufactured in an electrolyte containing sulfuric acid or perchloric acid, which was used as a supporting electrolyte. If boric acid was served as the supporting electrolyte, the morphology of the Pt particles were cubic structures instead of dendritic structures. Electrochemical characteristics of catalytic efficiency on the anode and cathode were investigated via cyclic voltammetry analysis in a sulfuric acid solution. Finally, a single cell test was also demonstrated.
(Invited) Photo-Electrochemical Water and CO2 Reduction Devices Operating Under Concentrated Radiation
Authors: Haussener Sophia 
Published: May 2020

Achieving high current densities while maintaining a high energy conversion efficiency is one of the main challenges for enhancing the economic competitiveness of solar fuel producing photo-electrochemical devices [1]. I will discuss two device implementations utilizing concentrated irradiation to achieve high current density operation. The water-splitting device is utilizing thermal integration to sustain high performance while dealing with high current density and the corresponding overpotentials [2]. I will quantify the theoretical increase in the maximum efficiencies at given current densities of photoelectrochemical devices resulting from thermal synergies. I will then discuss device implementation of such an approach and show how more realistic device models (multi-dimensional, multi-scale, multi-physics) can be used to support the device implementation and its operational understanding [3]. I will then show how the design principles developed for water splitting can be translated to CO2 reduction devices and discuss a corresponding device implementation.

References

1. M. Dumortier, S. Tembhurne, S. Haussener, Energy Environmental Science, 8: 3614-3628, 2015.
2. S. Tembhurne, F. Nandjou, S. Haussener, Nature Energy, 4: 399-407, 2019.
3. S. Tembhurne, S. Haussener, Journal of The Electrochemical Society, 163: H1008-H1018, 2016.
(Invited) SnS2 Thin Film and Powder for Artificial Photosynthesis
Authors: Chen Kuei-Hsien , Shown Indrajit , Reta Tadesse Billo , Wu Yu-Kai , Chen Li-Chyong 
Published: May 2020

Solar photoreduction of CO2 to produce value added hydrocarbons is highly desirable to tackle environmental and energy issues. [1-2] Despite the great improvement in the efficiency and cost of solar cells, the efficiency in artificial photosynthesis is much lower than the >15% of solar cells. Recent progress in 2D chalcogenides with tunable bandgap and layer numbers offers great opportunity for the investigation in this field. In this work, thin film and powder SnS2 have been synthesized for the study. Hydrothermal synthesis of carbon-containing SnS2 exhibits a highly active photocatalytic conversion of CO2 to selective hydrocarbons under visible-light irradiation. Overall, the carbon doping in the SnS2 nanostructure plays a key role and significantly enhance the visible light photocatalytic activity with a photochemical quantum efficiency above 0.7%. [3-4] Meanwhile, Thin film SnS2 has been grown for the mechanism study. By carbon-ion implantation of the thin film, we observed enhanced CO2 reduction under solar illumination. Other FTIR, Raman, NMR, BET, SECM, and synchrotron based facilities including APXPS and XAS have been used to investigate this issue.
1. Shown, H.C. Hsu, Y.C. Chang, C.H. Lin, P.K. Roy, A. Ganguly, C.H. Wang, J.K. Chang, C.I. Wu, L.C. Chen, K.H. Chen, Nano Letters
14, 6097-6103 (2014).
2. Billo, F.Y. Fu, P. Raghunath, I. Shown, W.F. Chen, H.T. Lien, T.H. Shen, J.F. Lee, M. C. Lin, J.S. Hwang, C.H. Lee, L.C. Chen, and K.H. Chen, Small
14, 1702928 (2018).
3. Shown, S. Samireddi, Y.C. Chang, R. Putikam, P.H. Chang, A. Sabbah, F.Y. Fu, W.F. Chen, C.I. Wu, T.Y. Yu, P.W. Chung, M.C. Lin, L.C. Chen, and K.H. Chen, Nature Comm.
9, 169 (2018).
4. Y. Fu, I. Shown, C.H. Li, P. Raghunath, T.Y. Lin, T. Billo, H.L. Wu, C.I. Wu, P.W. Chung, M.C. Lin, L.C. Chen, and K.H. Chen, ACS Appl. Mater. & Interface
11, 28 (2019).
Employing Non-Noble Metals As Catalysts for CO2 Electroreduction
Authors: Kumawat Adhidesh S. 
Published: May 2020

CO2 electroreduction to fuels is one of the most viable solutions for tackling both the issues of global warming and energy crises. It is due to the fact that the products such as formic acid, methanol, etc. which are obtained by electroreduction of CO2 could be employed as hydrogen carriers or directly as fuels. This phenomenon attracts huge research towards the process and its bottlenecks for making it commercial. The major hurdles regarding catalysis of CO2 electroreduction process are low solubility of CO2 in aqueous solutions and low product yields.
In our previous works, we have already demonstrated the employment of gas diffusion electrodes for non – noble metal catalysts such as Pb, Bi and Sn. The usage of gas diffusion electrodes enables us to exploit the three phase contact of CO2 gas – solid catalysts – liquid electrolyte and shows higher product (formate ion) yield.[1] Additionally, we have also shown through another work that the ternary eutectics of these three non – metal catalysts employed exhibits higher activity for CO2 electroreduction than singular pure metals or any other binary or ternary alloyed compositions of the metals.[2]

In this work, we want to exploit the conclusions from both the works and subject ternary alloy composition of Pb – Bi – Sn metals in gas diffusion electrode configuration for the process of CO2 electroreduction. Based on the previous two results, author believes that this would enable us to obtain higher product yield and hence better energy efficiency which would be a step forward towards sustainable development.
Reference:
[1] A. S. Kumawat and A. Sarkar (2017), Comparative study of carbon supported Pb, Bi and Sn catalysts for electroreduction of carbon dioxide in alkaline medium, Journal of Electrochemical Society, 164 (14), H1112 – H1120. doi: 10.1149/2.0991714jes
[2] A. S. Kumawat and A. Sarkar (2019), Electrochemical reduction of CO2 on Pb – Bi – Sn metal mixtures – Importance of Eutectics, SN Applied Sciences 1: 301. doi: 10.1007/s42452-019-0313-y
Influence of Surface States and Mobility on Charge Transport in BiVO4 Investigated By Surface Photovoltage Spectroscopy
Authors: Fengler Steffen , Emmler Thomas , Wolpert Charline , Schieda Mauricio , Villa Vidaller María , Klassen Thomas , Dittrich Thomas 
Published: May 2020

In order to enable mass production of photocatalytically active electrodes for direct conversion of solar energy into hydrogen, abundant materials and inexpensive preparation methods are needed. BiVO4 photoelectrodes prepared by aerosol deposition satisfy these requirements, in addition offering reasonable photocurrent densities, and can potentially contribute to the establishment of a prospective economy based on hydrogen as energy source.
Nevertheless, in order to allow the economically feasible implementation of BiVO4 electrodes for direct water splitting, there is need for further improvement of the electrodes efficiency.
In particular, an increased understanding of factors limiting the photocurrent is needed. In this work, BiVO4 photoelectrodes, prepared by aerosol deposition of BiVO4 particles on FTO-substrates, were investigated by surface photovoltage (SPV) as well as photocurrent and Mott-Schottky measurements.
Surface photovoltage spectroscopy under front and back illumination gives evidence of limitation of charge transport by a significant lower mobility of electrons compared to holes, leading to a nearly tenfold higher photocurrent, when illuminated from the back, compared to illumination from the front. Furthermore, the presence of traps for holes as well as for electrons on the BiVO4 surface has been confirmed by transient surface photovoltage spectroscopy and their influence on the photocurrent is discussed.

Figure 1
(Invited) In-Depth Understanding of Photoelectrochemical Water Splitting Systems By Operando Electrochemical Techniques
Authors: Tilley David 
Published: May 2020

In this talk, I will show how operando electrochemical techniques can be used to gain a deeper understanding of the underlying photophysical charge carrier processes taking place in photoelectrodes under practical water splitting conditions. High performance semiconductor-based electrodes are often multilayer systems (for maximizing the photovoltage, stability, etc.), and the relatively high number of interfaces in these devices makes characterization challenging. The characterization of both photocathodes and photoanodes will be discussed utilizing the dual working electrode (DWE) technique as well as photoelectrochemical impedance spectroscopy (PEIS). Using a certain architecture of DWE that preserves the catalytic interface, the performance of water splitting photoelectrodes can be de-convoluted to observe changes in the photovoltaic output separately from changes in the surface catalyst, rapidly identifying mechanisms of degradation in these systems.[1] This technique can also be used to detect the band position of the surface layer under operation in photoanode systems, which provided evidence for a certain mechanism of charge transfer.[2] Finally, I will show how PEIS can be used to characterize complex systems such as Au/Cu2O/Ga2O3/TiO2/RuOx, identifying the problematic interfaces in this promising system.[3]
[1] Cui, W.; Niu, W.; Wick-Joliat, R.; Moehl, T.; Tilley, S. D.* Operando Deconvolution of Photovoltaic and Electrocatalytic Performance in ALD TiO2 Protected Water Splitting Photocathodes Chem. Sci.,
2018,
9,6062-6067. doi: 10.1039/C8SC01453A

[2] Cui, W.; Moehl, T.; Siol, S.; Tilley, S. D.*
Operando electrochemical study of charge carrier processes in water splitting photoanodes protected by atomic layer deposited TiO2
Sustainable Energy Fuels
2019,
3, 3085 - 3092. doi: 10.1039/C9SE00399A

[3] Moehl, T.; Cui, W.; Wick-Joliat, R.; Tilley, S. D.* Resistance-based analysis of limiting interfaces in multilayer water splitting photocathodes by impedance spectroscopy Sustainable Energy Fuels,
2019, 3, 2067–2075. doi: 10.1039/C9SE00248K
(Invited) Strain Effects on Li Ion Conductivity – Migration, Defect Correlations, and Structural Changes
Authors: Zguns Pjotrs , Yildiz Bilge 
Published: May 2020

Elastic or plastic strain at cathode/electrolyte interfaces can affect the charge transfer kinetics in all-solid-state Li-ion batteries. Quantifying this effect both for Li ion conduction within the solid electrolyte material and for the Li transfer ability at the interface is important for understanding the kinetics of solid state batteries. Depending on the strain tensor, the impact could be beneficial or, alternatively, detrimental. While it is generally known that isotropic tensile strain increases the ionic conductivity and compressive strain decreases it [1], how different strain fields act upon Li ion conduction is not yet assessed. Existing studies show a non-trivial decrease/increase of Li-ion migration energies depending on relative alignment of migration direction and strain field [2], making quantitative estimates of conductivity changes difficult to predict. Here, we study the effect of strain on Li ion conductivity of β-Li3PS4 by means of Ab Initio Molecular Dynamics (AIMD) simulations. Ionic conductivity is directly calculated from AIMD trajectories using Nernst–Einstein equation, as it is linearly proportional to the diffusivity of the center-of-mass of all Li-ions [3]. Our calculations indicate that biaxial strain could substantially promote correlated motions of Li-ions, which in turn could increase ionic conductivity of β-Li3PS4. The effect depends on direction of applied strain, and the underlying structural changes increasing ionic conductivity are discussed.
[1] Y. Wang, W.D. Richards, S.P. Ong, L.J. Miara, J.C. Kim, Y. Mo and G. Ceder, Design principles for solid-state lithium superionic conductors, Nat. Mater.
14
, 1026–1031 (2015)
[2] C. O’Rourke and B. Morgan, Interfacial strain effects on lithium diffusion pathways in the spinel solid electrolyte Li-doped MgAl2O4, Phys. Rev. M
2, 045403 (2018)
[3] A. Marcolongo and N. Marzari, Ionic correlations and failure of Nernst-Einstein relation in solid-state electrolytes, Phys. Rev. M
1, 025402 (2017)