bluuebunny/crossref_metadata_2025 huggingface dataset:
Sulfide-Based Solid Electrolytes By Solution Processing
Authors: Lee Byoung-Sun , Xing Xing , Liu Haodong , Liu Ping
Published: February 2020

Solid electrolytes (SE) have been considered as alternative components to organic liquid electrolytes in lithium batteries (LIB). They promise safety enhancement by preventing the safety risks (e.g., leakage and ignition) [1]. In addition, the possibility of replacing graphite anode with lithium can lead to higher energy densities. Among various SE types, Li2S-P2S5 based sulfide SEs consisting of PSx polyhedral anions have been extensively explored due to its superionic conductive performances [2]. Previously, the SE was fabricated as pellets from Li2S-P2S5 powders via sintering or cold-pressing to reduce the grain boundary resistance. However, the processing costs of the high-energy ball milling and/or sintering at high temperature are considerable. In the meantime, the SE pellets are very thick (> 200 μm) due to the need to maintain mechanical integrity during processing and handling, resulting in cell energy density reduction, and the SE pellet brittleness prevents efficient device integration. Therefore, a desirable SE synthesis process should be designed to meet the following requirements: 1) low processing cost, 2) easy device integration, and 3) high energy density. In this work, we describe a Li2Sy-P2S5 solution coating process for the SE synthesis on the basis of aforementioned three requirements. Morphologies, compositions, crystal structures, and microstructures of the synthesized SE layers (Figure 1) were thoroughly examined using SEM, Raman spectroscopy, XRD, and XPS, and electrochemical performances were assessed using electrochemical impedance spectroscopy (EIS) and lithium ion battery cycling performance. We will describe how the fine tuning of solution composition and reaction condition can offer solid electrolyte layers inherently amenable to device integration.

[1] Teragawa, S. et al., J. Mater. Chem. A 2, 5095 (2014)

[2] Ohara, K. et al., Sci. Rep. 6, 21302 (2016)

Figure 1. Solution process based solid electrolyte (SE) layers formed on a metal electrode: a) photograph, and b) cross-sectional SEM image, and EDX images of c) phosphorus and d) sulfur in cross-section shown in b).

Figure 1
Mesoscale Computational Design of Heterogeneous Solid Electrolytes for Optimum Ionic Conductivity
Authors: Hu Jia-Mian , Ji Yanzhou , Wang Bo , Yang Tiannan , Chen Long-Qing
Published: February 2020

Heterogeneous solid electrolytes integrating two or more constituents (viz., phases, domains, and grains) may display a global ionic conductivity that is significantly superior to those of their homogeneous constituents. Many computational models and theories have been developed to understand the influence of microstructural features on the global ionic conductivity of these heterogeneous electrolytes. These model or theories typically utilize randomly packed spheres to represent second-phase fillers, however, random phase distributions are rare in practice because correlations always occur during materials processing or microstructure evolution. In this work, we develop a phase-field method based computational model that can generate 3D microstructure forming by phase separation instead of random packing, and predict both the global and local ionic conductivities of these microstructure informed by first-principles density functional theory (DFT) calculations. Using nanoporous Li3PS4 solid electrolytes as an example, the calculated global ionic conductivity agrees well with the experiments. The present model can therefore be utilized to generate databases of microstructure and corresponding properties for the next-step data-driven mesoscale computational design of heterogeneous solid electrolytes.
(Invited) Megawatt PEM Electrolyzers: from Laboratory to Market, a Road Map
Authors: Hamdan Monjid
Published: February 2020

Proton-exchange membrane (PEM)-based electrolysis is at the leading edge of a global energy system transformation. The energy vision of the future incorporates abundant renewable energy which is transformed into hydrogen for use in applications such as mobile refueling, power to gas, and grid-level energy storage. To meet these new market megatrends, PEM-based electrolyzer manufacturers are scaling-up their electrolyzer stack and system sizes with increased power capabilities (Figure 1).

This talk will focus on recent advancements in PEM-based stack technology, validation of subscale stacks and systems, and the eventual scale-up to Megawatt-scale hydrogen production; providing insight into PEM-based electrolyzer stack product development and scale-up strategies.

Giner, Inc. is a leading developer of PEM technologies and has extensive experience in the design and development of PEM-based electrolyzers, fuel cells and related electrochemical devices. Giner has continued the development of PEM-based electrolysis in the U.S., making significant advancements in stack efficiency, differential pressure operation, cost reduction, and scale-up. Our technology ranges from highly-reliable sub-scale electrolyzer stacks operating at a differential pressure of 5,000 psig to low-cost Megawatt electrolyzer stacks and systems operating at pressures of up to 600 psig for commercial applications.

The presentation will describe the efforts and requirements involved in testing, development, validation, and cost reduction, and will identify several areas of interest that have been implemented to further advanced PEM-based stack technology, including the development of innovative stack designs capable of high current density, and the scale-up of the electrolyzer stack to large active areas for Megawatt-scale hydrogen production.

Acknowledgements: The Author gratefully acknowledges financial support from the Department of Energy for the work described in this presentation.

Figure 1
(Invited) Electrochemical Atomic Layer Deposition of Ultrathin Electrocatalytic Films
Authors: Moffat Thomas P. , Ahn Sang Hyun , Liu Yihua , Bertocci Ugo , Gokcen Dincer , Ritzert Nicole L. , Wang Rongyue , Hangarter Carlos
Published: February 2020

Development of a sustainable hydrogen economy based on water electrolysis and fuel cells is constrained by the performance, longevity and high cost of Pt group electrocatalysts. Important strategies for improving catalytic reactivity include alloying, forming bimetallic or alloyed surfaces, and engineering substrate–catalyst interactions. At the same time, significant effort is underway to minimize the loading of Pt group metals by examining new synthesis methods and electrode geometries. Of particular interest is atomic layer deposition (ALD) for growing ultrathin films that maximize utilization of rare, expensive metals and facilitate the exploration of bimetallic effects in electrocatalysis.

Recently, an inexpensive “wet form” of ALD based on self-terminated electrodeposition reactions was uncovered that enables controlled formation of ultrathin films of Pt, Ir and iron group metals and alloys thereof. The mechanism of self-terminated deposition reactions will be discussed and the utility of these films as bimetallic electrocatalysts will be demonstrated. For example, monolayer equivalent Pt and Ir films were found to match or exceed the best known specific HER/HOR activity for bulk polycrystalline Pt or Ir electrodes and thereby offer the promise of increasing the scalability of these important precious metals in energy conversion devices.
(Invited) In-Situ investigation of Triple-Phase Boundary Electrochemical Reactions in PEM Electrolyzer Cells
Authors: Zhang Feng-Yuan
Published: February 2020

In-situ

Investigation of Triple-phase Boundary Electrochemical Reactions in PEM Electrolyzer Cells

Jingke Mo, Zhenye Kang, Gaoqiang Yang, Derrick Talley, and Feng-Yuan Zhang*

Nano HELP : Nanodynamics and High Efficiency Lab for Propulsion & Power

Department of Mechanical, Aerospace and Biomedical Engineering,

UT Space Institute, University of Tennessee, Knoxville

*fzhang@utk.edu

 

Abstract

Polymer electrolyte membrane electrolyzer cells (PEMECs) have been considered as one of the most effective and environment-friendly way for energy storage when coupled with renewable energy sources. In PEMECs, water is electrochemically split into oxygen and hydrogen. At the anode side, the circled water flows over the liquid/gas diffusion layer (LGDL) and diffuses to the triple-phase boundaries (TPBs) - the catalyst layers, where it is decomposed into oxygen, electrons, and protons. The proton will transport through the proton exchange membrane (PEM), reach the cathode catalyst layer, and form hydrogen at the cathode side. Due to limitations of the designs of conventional PEMECs and LGDLs, the microspatial and microtemporal scales of the electrochemical reactions, the phenomena of TPB electrochemical reactions has never been explored in operating PEMECs in-situ.

In this research, an innovatively designed transparent PEMEC was developed, and the thin and well-tuned titanium LGDLs with straight-throughout pores were fabricated. A high-speed and micro-scale visualization system (HMVS) was built for in-situ characterizations. The TPB electrochemical reactions only occurred at the edges adjacent to the good conductive materials. Visualization results reveal the real phenomena inside an operating PEMEC, which can not only help maximize the utilization of catalyst, but also help to optimize the fabrication of catalyst layer. The discovery will have a lot application on improving the electrochemical devices.
Liquid-Solid and Solid-Solid Interfaces in Electrocatalysis from First Principles
Authors: Zeng Zhenhua , Greeley Jeff
Published: February 2020

Understanding the electrochemical reactions at Liquid-Solid interfaces has been a great and long-term interest but challenge for both experimentalists and theorists. Even though tremendous advances have made through numerous techniques, significant uncertainties relating to the reaction intermediates and reaction mechanism remain. The problem is further complicated when a Solid-Solid interface has been formed either through electrodeposition or de-alloying, as the corresponding interface structures and consequently surface structures of the catalysts are still largely unknown.

In this talk, we will review the methodologies we have recently developed to de-convolute those effects, including a synergistic strategy towards highly accurate prediction of Pourbaix diagram of transition metal (hydroxy)oxides, a simple Morie pattern technique for screening Solid-Solid interface, ab initio molecular simulation to sample Liquid-Solid interfaces and X-ray Photoelectron Spectroscopy simulation to identify the oxygenated species at Liquid-Solid interface.

Next, using monolayer layer (hydroxy)oxide-metal interface as an example, we will demonstrate how the combination of the above techniques could identify the stable phases under various electrochemical conditions. As a case study, we will show the bi-functional role of the interface in promoting hydrogen evolution reaction (HER). As another example, we will show the development of the metal-metal interface during the de-alloying process of Pt-based alloy electrocatalysts.

Finally, we will show the applications of these understandings for the design of new catalysts with improved performances for electrolysis and fuel cell applications.

[1] L. Wang, Y. Zhu, Z. Zeng, C. Lin, M. Giroux, L. Jiang, Y. Han, J. Greeley, C. Wang, and J. Jin, Nano Energy 31, 456 (2017).

[2] Z. Zeng and J. Greeley, Nano Energy 29, 369 (2016).

[3] Y. Ha, Z. Zeng, Y. Cohen, J. Greeley, and A. A. Gewirth, J. Phys. Chem. C 120, 8674 (2016).

[4] Z. Zeng, M. K. Y. Chan, Z.-J. Zhao, J. Kubal, D. Fan, and J. Greeley, J. Phys. Chem. C 119, 18177 (2015).
Hollow Co3O4 Nanopolyhedrons Interwoven with Amorphous Nanowires for Enhanced Lithium Storage and Water Splitting
Authors: Xu Wangwang , Xie Zhiqiang , Wang Zi , Dietrich Grant , Wang Ying
Published: February 2020

Complex heterostructured nanomaterials receive tremendous attention due to their superior physical and chemical performances than single-structured materials. Nevertheless, it remains a great challenge to precisely control the composition (crystalline or amorphous), size and dimension of the building blocks of hierarchical nanostructures. Herein, we report a scalable method for fabricating crystalline-Co3O4-carbon@amorphous-FeOOH interwoven hollow polyhedrons through thermal treatment paired with solution-phase growth for application as anodes in new-generation lithium ion batteries. In this synthesis, well-defined Co3O4-carbon hollow polyhedrons serve as both oxidizing agent and growth platform for amorphous FeOOH nanowires. The obtained heterostructured hollow polyhedrons exhibit a high reversible capacity of 603 mAh/g after 100 cycles at the specific current of 200 mA/g, showing a capacity fading of only 0.158% per cycle between 10 to 100 cycles, much lower than that of pure Co3O4-carbon hollow polyhedrons (0.604%). When the specific current returns from 2000 mA/g to 50 mA/g, Co3O4-carbon@FeOOH heterostructure maintains a specific capacity of 1120 mAh/g, demonstrating remarkable cycleabilty and high rate capability. Such superior performance is attributed to the synergistic effect of integrated crystal and amorphous components as well as the unique interwoven heterostructure. The design of such an interwoven 3D frame architecture provides new opportunity for obtaining high-performance electrode materials in the field of energy storage.

Reference

Xu, W. W.; Xie, Z. Q.; Wang, Z.; Dietrich, G.; Wang, Y.; Interwoven heterostructural Co3O4–carbon@ FeOOH hollow polyhedrons with improved electrochemical performance. Journal of Materials Chemistry A, 2016, 4, 19011 - 19018
A Hybrid Material Based on Molybdenum Carbide and Nitrogen Doped Carbon for Electrochemical Hydrogen Evolution
Authors: Chakrabartty Sukanta , Raj C Retna
Published: February 2020

The increase in the global consumption of fossil fuel has adverse impact on the economy and environment. Alternate clean and sustainable energy sources are necessary to meet the future energy requirement. Hydrogen is a promising eco-friendly fuel alternative to the traditional fossil fuel. Hydrogen can be generated by photochemical, electrochemical and photoelectrochemical methods using suitable catalyst. Pt-based catalysts have been conventionally used for the electrochemical hydrogen evolution. However, the use of such catalyst is not encouraged due to high cost and scarcity of Pt. In recent years, several less expensive and earth-abundant electrocatalysts, such as transition metal chalcogenides, phosphides, nitrides and carbides have drawn much attention.1-2 Among them, transition metal carbide, particularly molybdenum carbide (Mo2C) received enormous attention. The electrocatalytic activity of Mo2C can be tuned by controlling the electronic structure, shapes, size and morphology. Achieving high catalytic activity at low overpotential is a main challenge with metal carbide-based electrocatalysts.

We demonstrate a new chemical route for the shape-controlled synthesis of a hybrid material derived from N-doped carbon and Mo2C (Mo2C-N-C) for the electrochemical hydrogen evolution reaction (HER) in acidic and basic medium. The synthetic procedure involves the facile complexation of Mo-precursor with cationic polymer, poly(diallyldimethyammonim chloride) (PDDA) and the subsequent carburization at 800 0C under optimized condition. The hybrid material was characterized by analytical techniques including XRD, XPS, Raman, TEM, etc. Electron microscopic measurements evidence the growth of nanowire bundles with length of 2-3 µm. The electrocatalytic activity was evaluated by recording the polarization curves in 0.5 M H2SO4 and 1 M KOH. We could achieve the benchmark current density of 10 mA/cm2 in acidic and alkaline pH at an overpotential of 136 and 183 mV, respectively. The catalytic performance is comparable to the existing Mo2C-based catalysts.3 The catalytic activity was further evaluated by calculating the Tafel analysis. A Tafel slope of 56 and 61 mV/dec was observed in acidic and alkaline pH, respectively. The Tafel analysis suggests that the electroctalytic hydrogen evolution involves Volmer-Heyrovsky mechanism. The hybrid material is highly durable and it retains its initial activity even after 1000 cycles. The superior performance can be explained by considering the surface morpholgy of Mo2C as well as the synergistic effect between the carbide catalyst and N-doped carbon.

References:

Zeng, M.; Li, Y. J. Mater. Chem. A
2015, 3, 14942−14962.

Zou, X.; Zhang, Y. Chem. Soc. Rev. 2015, 44, 5148–5180.

Gao, W.; Shi, Y.; Zhang, Y.; Zuo, L.; Lu, H.; Huang, Y.; Fan, W.; Liu, T. ACS Sustainable Chem. Eng.
2016, 4, 6313−6321.

Figure 1
Crystal Morphology of CuO-TiO2 Nanotubes and the Glycerol Concentration on the Photocatalytic Hydrogen Generation
Authors: Vu Thu Thi Hanh , Ton Trang Nu Quynh , Nguyen Nam Dang , Le Tu Thi Ngoc , Nguyen Vu Si Hoai
Published: February 2020

In this work, the CuO-TiO2 nanotubes with 3 wt.% CuO (CuO-TiO2 NTs) is prepared using the hydrothermal method and the wet-impregnation (WI) process with calcination post-treatments. The characteristics of the morphology and crystalline structure of CuO-TiO2 NTs are characterized by different characterization techniques including X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), … An off-line gas chromatograph equipped with thermal conductivity detector (TCD, HP 5890) is used to detect the presence of hydrogen gas under the visible light. The results indicate that the crystal morphology of CuO-TiO2 NTs specimens at different annealing temperatures effects on the performance of hydrogen generation. In addition, glycerol aqueous solution concentration variation could be controlled the amount of hydrogen generation under the visible light. Therefore, these phenomena can be applied to the clear energy field.

Keywords: Nanotubes, Glycerol, CuO, TiO2, Photocatalytic hydrogen generation.
Investigating the Role of Fe in Transition-Metal (Oxy)Hydroxide Electrocatalysts for the Oxygen Evolution Reaction
Authors: Enman Lisa J. , Stevens Michaela Burke , Batchellor Adam S. , Vise Ashlee E. , Boettcher Shannon W.
Published: February 2020

The efficiency of water electrolysis for hydrogen production is limited in part by the slow kinetics of the oxygen evolution reaction (OER).1,2 Nickel-iron and cobalt-iron (oxy)hydroxides have been shown to be the most active, low-cost electrocatalysts for the OER in alkaline conditions.3–5 Although it is evident that Fe is essential for high activity,6,7 its role in the catalytic active site is still largely debated.8,9 We investigate the role of Fe in NiOOH by comparing the effects of Ti, Mn, La, and Ce incorporation on the OER activity and electrochemical behavior of NiOOH in Fe-free 1 M KOH.10 We show that other metal cations in NiOOH can increase its reduction potential in a similar way to Fe, but without the same orders of magnitude increase in OER activity. This suggests that Ni is not likely the active site as its electronic properties are not correlated to activity. We also evaluate the OER activity and Tafel behavior of Fe3+ impurities on different noble metal substrates. We find that the activity varies by substrate suggesting that the local atomic and electronic structure of [FeO6] units play an important role in catalysis of the OER as it can be tuned by substrate interactions. Finally, through in situ and in operando X-ray absorption spectroscopy experiments, we find that the local structure around Fe atoms in Co(Fe)OOH changes during OER while that of Co stays the same. Given that the OER activity on a per Fe basis is independent of [Fe] in Co(Fe)OOH, the potential dependent structural changes further indicate that Fe is essential to the catalytic active site for the OER on transition-metal (oxy)hydroxides.

References

(1) Walter, M. G.; Warren, E. L.; McKone, J. R.; Boettcher, S. W.; Mi, Q.; Santori, E. A.; Lewis, N. S. Chem. Rev.
2010, 110(11), 6446.

(2) Ursua, A.; Gandia, L. M.; Sanchis, P. Proc. IEEE
2012, 100(2), 410.

(3) Trotochaud, L.; Ranney, J. K.; Williams, K. N.; Boettcher, S. W. J. Am. Chem. Soc.
2012, 134(41), 17253.

(4) Burke, M. S.; Zou, S.; Enman, L. J.; Kellon, J. E.; Gabor, C. A.; Pledger, E.; Boettcher, S. W. J. Phys. Chem. Lett.
2015, 6(18), 3737.

(5) Burke, M. S.; Enman, L. J.; Batchellor, A. S.; Zou, S.; Boettcher, S. W. Chem. Mater.
2015, 27(22), 7549.

(6) Corrigan, D. A. J. Electrochem. Soc.
1987, 134(2), 377.

(7) Trotochaud, L.; Young, S. L.; Ranney, J. K.; Boettcher, S. W. J. Am. Chem. Soc.
2014, 136(18), 6744.

(8) Friebel, D.; Louie, M. W.; Bajdich, M.; Sanwald, K. E.; Cai, Y.; Wise, A. M.; Cheng, M.-J.; Sokaras, D.; Weng, T.-C.; Alonso-Mori, R.; Davis, R. C.; Bargar, J. R.; Nørskov, J. K.; Nilsson, A.; Bell, A. T. J. Am. Chem. Soc.
2015, 137(3), 1305.

(9) Chen, J. Y. C.; Dang, L.; Liang, H.; Bi, W.; Gerken, J. B.; Jin, S.; Alp, E. E.; Stahl, S. S. J. Am. Chem. Soc.
2015, 137(48), 15090.

(10) Enman, L. J.; Burke, M. S.; Batchellor, A. S.; Boettcher, S. W. ACS Catal.
2016, 6 (4), 2416.
The Importance of Nickel Hydroxide Structure and Electrolyte Composition in the Kinetics of the Oxygen Evolution Reaction
Authors: Perini Nickson , Godoy João Victor , Ticianelli Edson Antonio
Published: February 2020

The production of molecular hydrogen from water electrolysis is a challenging issue mainly because of the sluggish kinetics of the oxygen evolution reaction (OER) and the low catalyst stability[1]. For alkaline electrolyzers, nickel hydroxides have been attracting attention due to their high activity for this reaction[2]. In this work, we have synthesized and characterized nickel hydroxide nanoparticles showing enhanced activity for the oxygen evolution reaction when compared to the state-of-art iridium oxide. This is probably due to its amorphous characteristic and the preferential formation of α-phase, confirmed by X-ray diffraction pattern and the cyclic voltammetric profile that presents a redox pair in the range of potential corresponding to the alpha phase (from -0.25 V to 0.45 V vs. normal hydrogen electrode)[3]. The effects of electrolyte composition, comprazing LiOH, NaOH and KOH, were also studied for the nickel hydroxides catalysts in comparison to gold electrode. The results have shown that the configuration of the active sites and thus the kinetics of the OER depend on the interaction between the species in the electrolyte and the catalyst surface.

Acknowledgements:
N.P. and E.T. acknowledge São Paulo Foundation (FAPESP) for financial support (grants No. 2015/18274-5 and 2013/16930-7)

References

[1] M.W. Kanan, D.G. Nocera, In situ formation of an oxygen-evolving catalyst in neutral water containing phosphate and Co2+., Science. 321 (2008) 1072–1075.

[2] O. Diaz-Morales, D. Ferrus-Suspedra, M.T.M. Koper, The importance of nickel oxyhydroxide deprotonation on its activity towards electrochemical water oxidation, Chem. Sci. 7 (2016) 2639–2645.

[3] J. Van Drunen, A.F.B. Barbosa, G. Tremiliosi-filho, The Formation of Surface Oxides on Nickel in Oxalate-Containing Alkaline Media, (2015) 481–491.
Tuning the Electrocatalytic Activity of Perovskite Electrocatalysts for Water Oxidation By Active Site Variation
Authors: Stevenson Keith J , Hardin William G. , Forslund Robin , Johnston Keith P.
Published: February 2020

Perovskites are a family of complex oxides with the nominal formula AMO3, where A is lathanide or alkali earth and M is typically a transition metal. They are of great interest as replacements for precious metals and oxides used in the oxygen evolution reaction (OER). Perovskite electrocatalysts have been shown to have greater specific activities than precious metals and their oxides, but high mass activities have not yet been realized due to the complex nature of perovskite oxide surfaces and inadequate synthesis techniques which often result in unwanted phase impurities and micron-scale materials. In this presentation we demonstrate the precise control over the chemical composition and structure of a series of perovskite and Ruddlesden-Popper electrocatalysts that are highly active for OER. The reaction pathways are perturbed by the direct modification of the perovskite structure by selective cation replacement and by promotion of catalyst-carbon support-interactions. Specifically the synthesis and electrochemical evaluation of a series of Ruddlesden-Popper (RP) La0.5Sr1.5Ni1-xFexO4+δ  will be reported that describe the highest catalytic activities reported for RP/perovskite matierials to date. These results will be described in the context of benchmarking to IrO2 and Pd and definition of the structure, electronic configuration and catalytic pathways. Electroanalytical techniques such as rotating disk electrochemistry and cyclic voltammetry are used in conjunction with materials characterization enabled by dynamic light scattering, electron microscopy, nitrogen sorption, X-ray photoelectron spectroscopy and X-ray diffraction. It will be demonstrated that these highly active perovskite catalysts are an emerging replacement for the precious metal catalysts.
(Invited) Transition Metal and Carbon Composites for Hydrogen Evolution Reaction at Universal Phs
Authors: Zhang Lulu , Shao Minhua
Published: February 2020

Owing to the climate change and shortage of fossil fuels, renewable energy sources such as solar and wind have become more and more attractive. However, these energies are intermittent and difficult to control. Water splitting provides hope to store these renewable energies in the form of hydrogen through a sustainable method. Up to now, the most popular cathodic electrocatalysts used in commercial solid polymer electrolyte (SPE) electrolyzers are still Pt-based materials that are highly scarce and costly. Therefore, one of the main challenges to generate hydrogen is to develop efficient and cost-effective catalysts toward hydrogen evolution reaction (HER) to replace Pt.

Non-precious metal and nitrogen co-doped carbon-based materials synthesized via different methods are explored for HER at universal pHs. It was found that the HER activity was highly dependent on the preparation method, type of transition metal/non-metal doping and compound formed. The lowest overpotential at 10 mA cm-2 was 190 mV in a 0.5 M H2SO4 solution at a catalyst loading of 0.255 mg cm-2 for Fe3C-C based composite. Density functional theory (DFT) calculations were applied to calculate the hydrogen binding energy and reaction barriers on various possible active sites. This talk will summarize recent systematic work on carbon-based composite materials for HER in my group.
Synergism and Implications of Using Carbon Supports with Perovskites for the Oxygen Evolution and Reduction Reaction
Authors: Stevenson Keith , Alexander Caleb , Abakumov Artem M. , Johnston Keith P.
Published: February 2020

Metal-Air batteries and fuel cells are a promising low-cost, high energy density storage solution to make sustainable energy resources and electric vehicles more economically viable than their fossil fuel counterparts. The major limitation that is preventing their widespread adoption are the slow kinetics of the oxygen evolution and reduction reaction which require large overpotentials to obtain reasonable current densities. Additionally, some of the best catalysts for the oxygen evolution and reduction reaction (OER and ORR) are precious metals like IrO2 and Pt respectively which make these devices impractical for large scale use. The most promising path to make a low cost highly bifunctional device is to combine two different catalysts that are separately optimized for the OER and ORR. We show that, by combining N-doped CNTs and LaNiO3, we can achieve a bifunctional window of 0.81 V at 10 and 3 mA/cm2
geo for the OER and ORR respectively at 51 μg/cm2 mass loading in 0.1M KOH at room temperature. We also show that carbon corrosion and transition metal dissolution can occur which have led to spurious OER currents to be reported in the literature. Future work should be aimed at increasing the stability of both electrode materials and focusing on developing catalysts that are optimized for either the OER or ORR to combine in a device.
Two-Dimensional Nanoframes As Bifunctional Oxygen Electrodes for Unitized Regenerative Fuel Cells
Authors: Rhodes Christopher , Godinez-Salomon Fernando , Archer Randall , Ying Yuanfang
Published: February 2020

Proton exchange membrane (PEM) fuel cells provide high efficiencies and clean power generation, however to enable wide scale adoption approaches are needed to reduce costs, improve durability, and provide on-demand hydrogen generation. Unitized regenerative fuel cells (URFCs) that combine power generation with fuel/oxidant generation within a single system can reduce costs and lower weight and volume compared with separate fuel cell and electrolyzer systems. Improved bifunctional oxygen electrodes (BOEs) that have lower overpotentials for oxygen reduction reaction (ORR) and oxygen evolution reactions (OER), higher stabilities for extended operating times, and lower costs are needed for URFCs. For extended durability, non-carbon-supported catalysts are required for BOEs since carbon oxidation occurs at high positive potentials leading to significant performance degradation.

Our group has demonstrated metallic two-dimensional (2D) nanoframes can be derived from controlled temperature/atmosphere treatments of metal hydroxide nanosheets. Metallic Ni-Pt 2D nanoframes exhibit a unique porous nanoarchitecture that allows the use of unsupported (carbon-free) electrodes that have shown significantly higher ORR activities and stabilities compared with Pt/C. Incorporation of Ir and/or Ru in an integrated 2D NiPtxMy (M=Ru, Ir) nanoframe was investigated to obtain bifunctional (ORR and OER) electrocatalyst nanoarchitectures. Electrochemical analysis of unsupported metallic 2D nanoframes using rotating disc electrode experiments shows that incorporating Ni within the structure significantly improves both ORR and OER activities. Further, we have investigated using transition metal oxide-supported catalysts to reduce the precious metal loading while maintaining high activity and stability. The ability to control the structure and properties of 2D nanoframes provides a route to develop bifunctional electrocatalysts with high activity, extended durability, and lower cost.
(Invited) Surface Composition and Structure Controlled High-Performance Electrohemicalcatalysts
Authors: Huang Yu , Zhao Zipeng , Li Mufan , Duan Xiangfeng
Published: February 2020

Noble metal-based nanocrystals have played important roles in heterogeneous catalysts due to their high activity and chemical stability. The high cost of noble metals, however, created roadblocks for the large volume production of noble metal catalysts for many applications. Improving the catalytic activity or the efficiency of noble metal usage, and prolong the life-time of a noble metal based catalysts are solutions to these challenges. On a nanocatalyst, the composition, atomic coordination, and strains of the top surface layers eventually determine its performance in catalytic reactions. Slight changes in the surface structure of catalytic materials for example, such as increase in the number of accessible surface adsorption sites or generating uniform surfaces with abundant specific defects, can have large impacts on the catalytic stability and activity. In this presentation I will share our recent efforts on tuning the surface compositions and structures of noble metal catalysts to improve both catalytic activity and stability.
Controlled Synthesis of Ptm (M=transition metal) Alloy Nanostructures Via Organic Solvents As High-Performance Oxygen Reduction Reaction Electrocatalysts
Authors: Shen Shuiyun , Wei Guanghua , Guo Yangge , Li Fan , Zhang Junliang
Published: February 2020

Controlled synthesis of PtM (M=transition metal) alloy nanostructures via organic solvents as high-performance oxygen reduction reaction electrocatalysts Shuiyun Shen, Guanghua Wei, Yangge Guo, Fan Li, Junliang Zhang*

Institute of Fuel Cells, MOE Key Laboratory of Power & Machinery Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Abstract: It is undoubted that to commercialize the polymer electrolyte membrane fuel cells (PEMFCs), there remains a great challenge to further improve the oxygen reduction reaction (ORR) activity on Pt. It has been proved that alloying Pt with transition metal (Fe, Co, Ni, and so on) will improve not only the activity but also the durability towards the ORR [1]. More importantly, it is also found that crystal plane-oriented PtM alloy nanoparticles or nanostructures show much higher ORR activity and durability [2]. In this work, we propose to synthesize PtM (M=transition metal) alloy electrocatalysts with controlled composition and structures via organic solvents. The as-obtained electrocatalysts will be investigated as the ORR electrocatalyst for PEMFCs.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (21373135, 21533005 and 21503134), and the Science Foundation of Ministry of Education of China (413064).

References

[1] Gasteiger, H. A.; Kocha, S. S.; Sompalli, B.; Wagner, F. T., Activity benchmarks and requirements for Pt, Pt-alloy, and non-Pt oxygen reduction catalysts for PEMFCs. Appl Catal B-Environ 2005, 56 (1-2), 9-35.

[2]  Chen, C.; Kang, Y.; Huo, Z.; Zhu, Z.; Huang, W.; Xin, H. L.; Snyder, J. D.; Li, D.; Herron, J. A.; Mavrikakis, M.; Chi, M.; More, K. L.; Li, Y.; Markovic, N. M.; Somorjai, G. A.; Yang, P.; Stamenkovic, V. R. Science 2014, 343, 1339-1343.
(Invited) Advanced Electrocatalysts of Polymer Electrolyte Membrane Fuel Cells
Authors: Song Yujiang
Published: February 2020

Advanced electrocatalysts are critical to polymer electrolyte membrane fuel cells (PEMFCs) and have apparently been influencing the widespread commercialization process of fuel cell cars in the world. As a matter of fact, currently, we are still confronting major issues for the development of desired electrocatalysts. In this talk, benchmark evaluation of electrocatalysts, platinum-based electrocatalysts for practical applications, non-platinum electrocatalysts toward alkaline hydrogen oxidation reaction and oxygen reduction reaction will be discussed.
Electrochemical Probing on Structural Changes of Surface Composition and Geometry of Ptni Nanoparticles with Pt-Enriched Surface
Authors: Jeon Tae-Yeol , Kim Sang-Kyung , Lee Hyun Hwi
Published: February 2020

Alloying Pt with M (M = Fe, Co, Ni, Cu, etc) has been extensively studied for increasing the oxygen reduction rate owing to the decreased bond strength of hydroxyl to Pt. Formation of Pt-enriched surface on the Pt-M alloy core can enhance both activity and durability, which generates several unique features that make it the most promising candidate for active and durable ORR catalyst, such as lower d-band center and consequent weaker bond strength of oxygen-containing adsorbates, and increased dissolution potential of surface Pt.

Our recent study on PtNi bimetallic nanoparticles with Pt-enriched surface for oxygen reduction reaction (ORR) will be presented with introducing conceptual understanding of electronic modification induced by the formation of Pt skin on PtM alloy.1 In particular, it will be discussed that the electrochemical properties, which were obtained from CO and reduced CO2 adlayer oxidation measurements before and after potential cycling under ORR conditions, provide us important informations for estimating the surface electronic and geometric states of pure Pt, PtNi, and Pt-enriched PtNi.

1. Jeon, T.-Y., Kim, S. K., Pinna, N., Sharma, A., Park, J., Lee, S. Y., Lee, H. C., Kang, S.-W., Lee, H.-K., Lee, H. H. Chem. Mater.
2016, 28, 1879-1887.
(Invited) Controlling Fuel Crossover and Hydration in Ultra-Thin Proton Exchange Membrane Based Fuel Cells Using Pt-Nanosheet Catalysts
Authors: Gao Ping
Published: February 2020

An ultra-thin proton exchange membrane (PEM) with Pt-nanosheet catalysts was designed for a self-humidifying fuel cell running on hydrogen and oxygen with 0% relative humidity. In this design, an ultra-thin Nafion membrane was used to reduce ohmic resistance. Pt nanocatalysts were uniformly anchored on exfoliated layered double hydroxide (LDH) nanosheets by chemical vapor deposition (CVD). After embedding Pt-LDHs nanocatalysts in 9 µm thick Nafion membranes, exfoliated LDH nanosheets effectively captured crossovered hydrogen and oxygen through membranes. Meanwhile, Pt nanocatalysts on LDH nanosheets catalyzed reactions between captured hydrogen and oxygen and provided in-situ hydration inside Nafion membranes to maintain theirs proton conductivity level. Furthermore, LDH nanosheets reinforced Nafion membranes with 162% improvement in tensile modulus and 126% improvement in yield strength. In a hydrogen fuel cell running with dry fuels, the MEA employing Pt-LDHs/Nafion membrane showed an improvement of 250 % in maximum power density, an increase of 300 % in current density at 0.3V and an improvement of 900 % in current density at 0.5V as compared to those of the MEA with a commercial Nafion 112 membrane. Furthermore, fuel cell tests were conducted on the PEMs with the thickness of 25 μm to observe the synergic effects of self-humidification and the suppression of fuel crossover. Compared to the commercial Nafion 211 membrane, Pt-LDHs/Nafion membrane with a thickness of 25 μm exhibited a combination of desirable properties for the development of affordable and durable hydrogen fuel cell technology, including better mechanical properties, higher open-circuit voltage (OCV), lower ohmic resistance and enhanced water management in a hydrogen fuel cell without external humidification.
Elucidating Structure-Activity Relationships for the Oxygen Reduction Reaction at Mn-Based Perovskites
Authors: Fermin David , Celorrio Veronica
Published: February 2020

Transition metal oxides such as perovskites (ABO3) are becoming an important class of materials in the context of oxygen electrocatalysis for alkaline fuel cells and metal-air batteries.1,2 Although these materials have been extensively investigated in the field of solid oxide fuel cells, their properties as oxygen electrocatalysts at room temperature are far from being fully rationalised. Establishing structure-activity relationships based on the electronic structure of the B-site, widely recognised as the main active site, is one of the key challenge in this field. Such information is extremely important towards designing catalysts with optimal B-site orbital occupancy, coordination number and metal-oxygen bond length.

In a recent study, we have shown that LaMnO3 exhibits over two orders of magnitude higher activity towards the ORR than other lanthanide perovskites (e.g. Co, Fe, Cr and Ni).3 Our analysis show that the origin of this high activity is linked to changes in the redox state at the Mn sites at potentials close to the formal ORR potential, leading to an increase in electron population at the key active site.

In this contribution, we shall focus on the structure-activity relationship of a family of LaxCa1-xMnO3 nanoparticles, assessing their activity as a function of the Mn-valency. We will provide a detailed analysis of the bulk and surface structure employing X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge spectroscopy (XANES). Studies employing rotating ring-disc electrodes of the nanoparticles supported on mesoporous carbon films show that their activity towards the ORR are among the highest reported for transition metal oxides.4 We finally establish that the mean ORR activity of surface Mn sites increases as the Mn valency decreases.5 These studies highlight the need for independent assessment of key aspects such as the extent of A-site surface segregation and average Mn valency in order to establish consistent structure-activity relationships.

References:

1- A. Grimaud et al. Nat. Mater. 2016, 15, 121

2- J. Suntivich et al. Nat. Chem. 2011, 3, 647

3- V. Celorrio et al. ChemElectroChem 2016, 3, 283

4- K.A. Stoerzinger, ACS Catalysis 2015, 5, 6021

5- V. Celorrio et al. Catal. Sci. & Technol. 2016, 6, 7231
(Invited) Membrane and Catalysts for Hydroxide Exchange Membrane Fuel Cells
Authors: Yan Yushan
Published: February 2020

Hydroxide exchange membrane fuel cells can work with PGM-free catalysts and are thus potentially economically viable. In the presentation i will show our recent work on the development of the hydrogen oxidation catalysts and the polymer hydroxide exchange membranes.
Dynamic Reaction Phenomena during Electrochemical Reduction of CO to Hydrocarbons on Copper
Authors: Trimarco Daniel Bøndergaard , Scott Søren B. , Bodin Anders , Sørensen Jakob E. , Mazzanti Nicola , Bagger Alexander , Pedersen Thomas , Hansen Ole , Chorkendorff Ib , Rossmeisl Jan , Vesborg Peter C. K. , Stephens Ifan E. L.
Published: February 2020

We have recently developed a unique vacuum inlet system, which couples a mass spectrometer to an electrochemical experiment like a conventional DEMS/OLEMS system – but with an unprecedented combination of quantitative and ultrasensitive product detection with sub-second time resolution. [1]

Using this one-of-a-kind tool, we experimentally map out the behavior of Cu-based CO reduction. In particular, we study transient overproduction of methane. We find that a very pronounced, overproduction of methane (compared to ethylene) is the result of an electrochemical pre-treatment of the catalyst with molecular oxygen dissolved in the electrolyte. Mechanistic implications are discussed.

[1] D. B. Trimarco et al., Rev. Sci. Instrum. 86, 075006 (2015)

Figure 1
Catalysts Facet Orientation and Surface Modifications for Improved Activity of Alcohol Oxidation
Authors: Li Meng , Adzic Radoslav R
Published: February 2020

Many problems encountered in hydrogen-fuel-cell technology, particularly those of hydrogen storage and distribution, can be circumvented by replacing hydrogen with liquid fuels, such as methanol and ethanol. However, the electrocatalytic oxidation reactions of methanol and ethanol are slow and incomplete even on the best existing Pt-based catalysts, which greatly impeded the wide-spread application of direct alcohol fuel cell (DAFC).

Our group demonstrated that one class of surfaces can be very active for the oxidation of methanol and ethanol [1]. These electrocatalysts consist of one Pt monolayer (PtML) under tensile strain when placed on extended or nanoparticle surfaces. Their activity and selectivity can be controlled with Pt-support interaction. Our experimental and DFT studies demonstrated a correlation between the strain induced by PtML-support interaction and the catalytic activity. Significant enhancement in the activity associated with the tensile strain and decreased activity associated with the compressive strain.

Most recently, we deposited PtML on Au single crystals and shape-controlled nanocrystals enclosed with different crystallographic facets[1,2], and electrochemical behaviors (Figure 1a) suggested that the deposited PtML possessed facets matching to the underlying Au. Surface structure can determine catalytic properties and a large density of atomic steps on high-index facets is especially desirable for breaking chemical bonds such as C-C bond splitting in ethanol total oxidation. Such property of translating facet-specific features from substrates to the supported PtMLopens new opportunities to enhance catalytic performances.

Another approach to improve activity involves modifying PtML surfaces with different co-catalysts. For example, Ru modified PtML/Au showed significantly enhanced activity for methanol oxidation and FTIR studies demonstrated that no adsorbed CO was formed during the reaction. The incorporation of co-catalysts such as Rh, Ir and Sn with PtML shifted onset potential of ethanol oxidation to more negative values (Figure 1b) and promoted a complete oxidation of ethanol to CO2.

Details of electrochemical, structural and spectroscopic studies, discussion of reaction mechanisms and possibilities of these findings to resolve the major impediment hindering the development of practical DAFCs and to open new studies of C-C bond splitting in variety of important reactions will be presented in the meeting.

Acknowledgements

This work was financially supported by the US DOE, Office of Basic Energy Science, Material Science and Engineering Division, Division of Chemical Sciences, Geosciences and Biosciences Division (Contract No. DE-SC0012704).

References

[1] M. Li, P. Liu, R. R. Adzic, J. Phys. Chem. Lett. 
2012, 3, 3480−3485.

[2] F. Lu, Y. Zhang, L. Zhang, Y. Zhang, J. X. Wang, R. R. Adzic, E. A. Stach, O. Gang, J. Am. Chem. Soc. 
2011, 133, 18074–18077.

Figure 1
Specific Metal-Polyoxometallate Interactions in Electrocatalysis, Photoelectrochemistry and Efficient Charge Propagation
Authors: Kulesza Pawel J
Published: February 2020

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of carbon nanostructures and noble metal nanoparticles, their stabilization and intentional activation, as well as organization into two-dimensional arrays, ultra-thin films or three-dimensional networks (e.g. through sequential attraction) on electrode surfaces. They can form nanosized materials with well-defined composition, structure and thickness that exhibit electrocatalytic properties toward oxidation of methanol, ethanol or dimethyl ether. We explore here the ability of inorganic structures to stabilize and derivatize metal and carbon nanostructures. Here certain nanostructured inorganic oxides (e.g. WO3, MoO3, TiO2, ZrO2, V2O5, and CeO2) and polyoxometallates of molybdenum or tungsten influence supported metal centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles thus affecting their chemisorptive and catalytic properties. Metal oxide nanospecies can generate –OH groups at low potentials that induce oxidation of passivating CO adsorbates (e.g. on Pt); they can potentially break C-H or C-O bonds (e.g. by hydrogen tungsten oxide bronzes); and they can possibly weaken C-C bonds during ethanol oxidation (e.g. through changes of the electronic properties of Pt).

Our research interests also concern development of systems for reduction of carbon dioxide. For example, instead of conventional Pd nanoparticles, nanosized Pd immobilized within ultra-thin films of polyoxometallates and their salts have been considered. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities. Among important issues are specific interactions between hydroxyl and metal-oxo centers and metallic palladium sites at the electrocatalytic interface.

When it comes to photoelectrochemical water splitting, we demonstrate here utility of gold nanoparticles (modified or stabilized with Keggin-type and ruthenium-containing polyoxometallates, PMo12O40
3-, as capping agents) to enhance photocurrents generated by mesoporous tungsten trioxide, WO3, photoanodes irradiated with visible light in aqueous solutions. To demonstrate generation of localized surface plasmons, we have performed measurements using scanning near-field optical microscope (SNOM). The mechanism for the interaction between the gold plasmons and the semiconductor is complex but sound.