bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability Enhancement of the Interaction Between Pt Nanoparticles and Carbon Supports through Carbon Surface Functionalization
Authors: Xin Le , Yang Fan , Li Zhe-Fei , Sun Chengjun , Stanciu Lia , Xie Jian 
Published: February 2020

Proton exchange membrane fuel cells (PEMFCs) that use hydrogen and oxygen in air as fuels to produce electricity have attracted extensive interests over the past decades.1 The high efficiency and zero emission make PEMFCs promising candidates for viable propulsive systems in electric automobiles.2 One of the major challenges that hinder the commercialization of PEMFCs vehicles is the poor stability of Pt nanoparticles on carbon supports, which mainly due to the dissolution and re-deposition of Pt and migration of Pt over carbon supports.3
4Both of them will cause the agglomeration of Pt nanoparticles, resulting in loss of Pt electrochemical surface area (ECSA) and the increasing of activation overpotentials.
Aiming to minimize the growth of Pt nanoparticles due to the Pt migration on carbon supports, fundamental understanding of their interaction is required, so as to modify the carbon supports to enhance the binding energy between Pt and carbons. In our recent work, Pt of 3% to 5% loading was deposited on XC-72 carbon black, graphene, functionalized XC-72 carbon black and functionalized graphene, where the Pt clusters or islands of about 3-6 atoms thickness on different supports can be achieved by a general two step method. The dispersion and morphology of Pt on pristine graphene, SO3H-graphene and NH2-graphene were then characterized by high resolution transmission electron microscopy (HRTEM). It is clearly shown that spherical Pt nanoparticles of very small size were uniformed dispersed on functionalized graphene, whereas on pristine graphene, some rod-like Pt crystals were observed. It indicates that the presence of functional groups prevents the migration of Pt nuclei on the two-dimentional graphene sheet during the synthetic process. X-ray absorption near edge structure (XANES) of Pt L-edge and C K-edge were performed to further characterize the interaction between Pt and different supports. The increasing of the intensity of the Pt L-edge adsorption peak compared with unsupported Pt suggests electron withdrawn from Pt to carbon supports might exists between Pt and carbon supports and the interaction strength follows the order of Pt/SO3H-Graphene > Pt/SO3H-XC72 carbon black > Pt/Graphene > Pt/XC72 carbon black. On the other hand, the shift of Pt L-edge adsorption peak to higher photon energy also indicates the possible increase of oxidation state of Pt due to the Pt-C interaction. This study will shed light on the strategy to improve not only the durability but also activity of Pt based catalysts in fuel cells.
(1) Gasteiger, H. A.; Markovic, N. M. Science
2009, 324, 48.
(2) Debe, M. K. Nature
2012, 486, 43.
(3) Xie, J.; Wood, D. L.; More, K. L.; Atanassov, P.; Borup, R. L. Journal of The Electrochemical Society
2005, 152, A1011.
(4) Shao-Horn, Y.; Sheng, W. C.; Chen, S.; Ferreira, P. J.; Holby, E. F.; Morgan, D. Topics in Catalysis
2007, 46, 285.
PEM Water Electrolysis - Durability Under Heavily Reduced Anode Catalyst Loading
Authors: Rakousky Christoph , Carmo Marcelo , Maier Wiebke , Stolten Detlef 
Published: February 2020

When coupled to renewable but nonetheless intermittent power sources such as wind or solar, polymer electrolyte membrane (PEM) electrolyzers are intended to be in operation for tens of thousands of hours1. Hence, the long term behavior of membrane electrode assemblies (MEAs) under these power operating characteristics is of great importance. At moderate conditions (25 cell stack, around 50°C and 1.3 A/cm²)2, commercial PEM electrolyzers show little to no significant degradation (< 4 µVh) after 55,000 h2. However the anode catalyst loading in commercial systems is generally high (> 2 mg/cm²)3 and the state-of-the-art catalyst material, iridium, is expensive and rare. A reduced catalyst loading will contribute to reduce the costs of electrolyzer stacks, but to this date the effect of anode catalyst loading on the durability of PEM electrolysis has not yet been thoroughly investigated in literature.
This study aims to show the durability of PEM electrolysis single cells under reduced anodic catalyst loadings. As shown in Fig. 1 (top), with IrO2 loadings as low as 0.6 mg/cm² we were able to reach identical performance when compared to our standard catalyst loading of 2.25 mg/cm² IrO2. Moreover, stable cell performances over 680 h in an initial life time test were obtained (Fig. 1 bottom). Further reductions in catalyst loading show deteriorating cell performances in 1000 h long term testing. In this study the performance degradation data of MEAs with lower anode loadings were shown and the degradation effects differentiated. The degradation characteristics were also partially localized using electrochemical impedance spectroscopy and reference electrode measurements4 in order to separate cathodic and anodic overvoltages.
We aim to contribute to the understanding of the degradation mechanisms and to possible cost reductions of MEAs for PEM electrolysis by showing the relation between anode loading and long term stability. This information shall assist in making PEM water electrolysis both cost effective and durable.

Fig. 1: Top: single cell performance under a heavily reduced anode loading of 0,60 mg/cm² IrO2. We were able to obtain similar cell performances as for the regular loadings of 2,25 mg/cm² IrO2 and stable cell performances over time (bottom).

References:

1. M. Carmo, D. Fritz, J. Mergel and D. Stolten, International Journal of Hydrogen Energy, 38, 4901-4934 (2013)
2. K. Ayers, PEM Electrolysis R&D Webinar, presented at the DOE Fuel Cell Technologies Program Webinar, May 23 (2011)
3. Debe, M. K.; Hendricks, S. M.; Vernstrom, G. D.; Meyers, M.; Brostrom, M.; Stephens, M. et al.:. In: J. Electrochem. Soc. 159 (6) (2012)
4. Jung, Myunghee; van Zee, John W., 216th ECS Meeting, 1585–1593 (2009)

Figure 1
Novel Hyperbranched Polymer-Based Anion-Exchange Membranes
Authors: Movil-Cabrera Omar , Frank Logan , Staser John A 
Published: February 2020

Anion-exchange membranes (AEMs) are promising materials for a wide variety of applications including among others, fuel cells, electrolyzers, and membrane separation processes. However, development of AEMs with improved hydroxyl conductivity and selectivity as well as excellent thermo-mechanical stability, remains an absolute necessity, now more urgent than ever, due to the global climate change and energy crisis.
The main objective of the present study is to synthesize novel AEMs with excellent hydroxyl conductivity and mechanical stability from hyperbranched polyester polymers. More specifically, poly (vinyl pyridine) (PVP) was grafted onto bis-MPA polyester-64-hydroxyl via graft copolymerization and subsequently quaternized using different alkylating agents. The effects of some variables such as grafting degree and alkylating agent on the morphology as well as on the materials properties of these new-developed membranes were evaluated. The cation stability in alkaline media and the water uptake of these AEMs were also investigated. Some characterization techniques such as NMR, SAXS, FTIR, TEM, TGA, DSC and impedance spectroscopy were used to assess the materials properties of these membranes.
(Invited) How Surface Ionic & Electronic Point Defects Control Oxygen Exchange Reactions
Authors: Chueh William C 
Published: February 2020

Surface electrochemical reactions are ubiquitous in many energy conversion systems. Of immense interests are solid-state electrochemical reactions that occur at the solid/gas interface in oxide electro-catalysts, such as those in oxygen-ion-conducting solid-oxide fuel cells and electrolyzers. Unlike their liquid counterparts, these electrochemical reactions involve the simultaneous transfer of ions and electrons between the solid and the gas. As such, the electro-catalysts need to catalyze both the oxygen-ion-insertion and electron-transfer reactions.
Under reaction conditions, perovskite oxides such as lanthanum ferrites and fluorite oxides such as cerium oxides gain and lose significant amounts of oxygen. It is well known that oxygen nonstoichiometry control a vast number of properties in oxides, such as magnetism, the formation of 2-D electron gas at heterojunction, and catalysis. Yet, the role of surface oxygen nonstoichiometry in electrochemical reactions remains largely a mystery due to difficulties in controlling and quantifying oxygen and valence electrons on the surface.
The fundamental question here is how does the surface oxygen nonstoichiometry control the electro-catalytic activity of oxides. In this talk, I will present operando spectroscopic investigations of cerium oxide and transition metal perovskite oxide surfaces using X-rays. We directly probed occupied and unoccupied electronic states using surface sensitive techniques under reaction conditions, that is, under high temperature, pressure and bias.
Anode-Supported Solid Oxide Fuel Cells Fabricated By Single-Step Reduced-Temperature Co-Firing
Authors: Wang Hongqian , Gao Zhan , Jakus Adam E , Shah Ramille N , Barnett Scott A 
Published: February 2020

Anode-supported solid oxide fuel cells (SOFCs) consisting of NiO-Y0.16Zr0.92O2-δ (YSZ) anode support layer, NiO-YSZ anode functional layer, YSZ electrolyte and (La0.8Sr0.2)0.98MnO3-δ (LSM)-YSZ cathode were successfully fabricated by single-step co-firing at 1250oC, 150oC lower than the usual 1400oC, with the addition of 1mol% Fe2O3 as sintering aid. Two different ceramic processing strategies - tape casting and colloidal deposition - were utilized for the fabrication. For the colloidally deposited cells, open-circuit voltages (OCVs) were near theoretical values for all cells. The cell yields maximum power density of 975 mW/cm2 and area specific resistance of 0.34 Wcm2 at 800oC. For the tape casted cells, a replica technique utilizing a graphite layer was incorporated to protect the cell during lamination, which improved the cell performance with maximum power density from 325 mW/cm2 to 650 mW/cm2 at 800oC. The effect of oxygen partial pressures on the cathode performance and hydrogen partial pressures on the anode performance was investigated using electrochemical impedance spectroscopy (EIS), and the results on the main limiting mechanisms will be discussed. Scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDS) showed no element transport between each layer during sintering process. The correlation between electrode microstructure and cell performance will be discussed.
Single-step firing is interesting in general to reduce the number of cell processing steps, but is also interesting for fabricating entire stack structures that can be co-fired together. Preliminary results will be presented on single-step reduced-temperature co-firing of stack structures fabricated by a combination of tape casting and direct ink write three-dimensional (3-D) printing.
In Situ X-Ray Absorption Spectroscopy for Batteries: Discovery of New Mechanisms and Materials
Authors: Segre Carlo U , Katsoudas John P. , Timofeeva Elena V. , Ramani Vijay K , Singh Dileep , Pelliccione Christopher J. , Ding Yujia , Aryal Shankar , Beaver Nathaniel M. , Li Yue , Sen Sujat 
Published: February 2020

Development of transformational electrochemical energy storage technologies is an imperative for enabling sustainable technologies such as vehicle electrification and renewable energy generation. Major advances in these technologies are made possible by developing the ability to predict how structural changes correlate with the functionality of new materials.
Characterization by x-ray absorption spectroscopy (XAS) is an important tool in developing a better understanding of the structure-function relationship in battery materials, including structural changes upon cycling and aging mechanisms. XAS is commonly used to study electrochemical reactions in situ and is particularly valuable when working with nanomaterials or highly disordered or doped crystalline systems. A successful in situ XAS experiment on battery materials requires a careful choice of experimental conditions including design of the in situ cell, choice of beamline, energy scan mode, and detectors. An overview of these considerations for various types of battery materials will be presented along with results which illustrate the pitfalls inherent in these experiments.
Results will be presented on a variety of Li-ion battery cathode and anode materials, including metals and metal oxides where there is a high capacity but rapid aging due to severe swelling of the anode material upon lithiation. Our results have identified the structural signature of metal-Li bonds and their persistence upon discharge, which imply a loss of electrical contact as the primary failure mode of these materials. In situ results on aqueous battery materials such as Fe2O3 and NiOOH will also be presented and discussed with particular emphasis on the comparison between nanoparticles in solid state electrodes and in nanofluid suspension electrodes known as nanoelectrofuel (NEF). NEF are stable dispersions of battery active nanoparticles in electrolyte that effectively charge/discharge as they are pumped through custom-designed flow cell(s) and represent a high-energy-density rechargeable, renewable, and recyclable electrochemical fuel.
(Invited) Enabling Oxygen Electrocatalysis for Sustainable Energy
Authors: Shao-Horn Yang 
Published: February 2020

The development of sustainable energy is one of the most important scientific challenges in the 21st century. A critical element for sustainable energy implementation is to have efficient energy conversion and storage. Oxygen electrocatalysis is central to enable photoelectrochemical and electrolytic water-splitting, fuel cells, and metal-air batteries. Probing a fundamental catalyst “design” principle” that links surface structure and chemistry to the catalytic activity can guide the search for highly active catalysts that are cost effective and abundant in nature. While such a design concept exists for metal catalysts, little is known about the design principles for oxygen electrocatalysis on oxides. Recent advances in identifying the design principles and activity descriptors of transition metal oxides will be presented. We will show that these fundamental concepts can be used to tune transition metal oxide surfaces with much enhanced catalytic activities. Moreover, we will discuss how oxide bulk electronic structures can influence the catalytic activities of oxides, from which two different reaction mechanisms are proposed. Lastly, connecting bulk to surface electronic structures is challenging but much needed to provide mechanistic insights, and some in-situ synchrotron X-ray measurements to this end will be discussed.
(La,Sr)CoO3-Rgo Hybrid Oxygen Reduction Reaction/Oxygen Evolution Reaction Bifunctional Catalyst
Authors: Chung Hoon T , Gao Wei , Higgins Drew Christopher , Martinez Ulises , Mukundan Rangachary , Tylus Urszula , Dumont Joseph H , Purdy Geraldine M , Dattelbaum Andrew M , Zelenay Piotr 
Published: February 2020

A bifunctional oxygen reduction reaction (ORR)/ oxygen evolution reaction (OER) catalyst is essential for rechargeable metal-air batteries and regenerative fuel cells. Platinum (Pt) and iridium oxide (IrO2) are the state-of-the-art ORR and OER catalysts, respectively. However the high price and scarcity of these platinum group metals (PGMs) has been an obstacle for wide spread application of these catalysts. Recently, in alkaline media, carbon based ORR and perovskite OER catalysts have demonstrated similar or even better catalytic activities compared to the counterpart PGM catalysts [1, 2]. Therefore, if we combine these two non-PGM catalysts, a non-PGM bifunctional ORR/OER catalyst can be obtained. A hindrance in this approach is the vulnerability of carbon-based ORR catalysts to oxidation in the OER potential range, i.e., potentials > 1.5 V vs. RHE. Thus development of robust ORR catalysts under practical OER conditions is a key to realize this kind of bifunctional catalysts.
The carbon support used in our ORR catalysts was black pearl (BP) 2000 [1]. In preliminary tests, however, we found that BP 2000 undergoes oxidization at potentials around ca. 1.2 V vs. RHE and above (data not shown). In this work, we used reduced graphene oxide (rGO) as an alternative support to synthesize oxidation resistant ORR catalysts. The OER catalyst we chose was a perovskite (La1-xSrx)CoO3-δ (LSC). Pre-synthesized LSC was added into the initial solution of the rGO based ORR catalyst synthesis process, and after drying and heat-treatment, bifunctional (LSC + rGO) catalysts were obtained. In measuring the OER activity of the LSC catalyst, acetylene black (AB) carbon was added to the LSC (LSC + AB) to increase the electrical conductivity. Fig. 1 shows the comparison of ORR/OER activities between (LSC + AB) and (LSC + rGO). As expected, the ORR activity of (LSC + rGO) is greatly improved by ca. 200 mV in terms of E½
, in comparison to that of (LSC + AB). Interestingly even the OER activity of (LSC + rGO) becomes higher than that of (LSC + AB). Thanks to the enhancement of both ORR and OER activities with (LSC + rGO), highly active bifunctional catalysts are obtained. In this talk, material analysis results and diverse electrochemical performances of the (LSC + rGO) catalysts will be presented.

Acknowledgements

Support from the Directed Research of the Los Alamos National Laboratory’s Laboratory Directed Research & Development (LDRD-DR) is greatly acknowledged.

References

Chung et al., Nat. Commun. 4, 1922 (2013).

Suntivich et al., Science, 334, 1383 (2011).

Figure 1
Enhanced Electrocatalytic Activity of Sm2O3-doped Ni-Co Coating Electrode for Hydrogen Evolution Reaction
Authors: Ding Shuangshuang , He Ping , Feng Wanru , Zhang Guangli , Zhang Susu 
Published: February 2020

Direct electrochemical splitting of water is an attractive method to generate the renewable energy carrier hydrogen [1]. Low-cost catalyst for hydrogen evolution reaction (HER) is one key step in this process [2]. So far, there are no other pure metals except for noble elements really showing high activities for HER, and many efforts have been made to look for highly catalytic activated transition metal based alloys for HER [3,4].
In this work, HER was investigated on Ni-Co alloy electrode and Ni-Co-Sm2O3 composite electrode in 0.50 M Na2SO4 + 0.10 M H2SO4 solution. It was indicated that Sm2O3 particles promoted the formation of an amorphous structure of Ni-Co alloy coating, which was benefit for HER. The surface of Ni-Co-Sm2O3 composites was more coarse and grainy compared with that of Ni-Co alloy layer (Fig. 1). Steady-state polarization curves (Fig. 2) showed that the hydrogen evolution potential of Ni-Co-Sm2O3 composite electrode positively moved by about 240 mV at 8.0 mA cm-2 compared with that of Ni-Co alloy electrode, indicating that the embedded Sm2O3 particles enhanced the electrocatalytic activity of Ni-Co coating for HER. Furthermore, Ni-Co-Sm2O3 composite electrode has considerably lower charge transfer resistance and higher exchange current density.

References

[1] C. Lupi, A. Dell’Era, M. Pasquali. In situ activation with Mo of Ni-Co alloys for hydrogen evolution reaction. International Journal of Hydrogen Energy, 2014, 39: 1932-1940
[2] Wei Cui, Chenjiao Ge, Zhicai Xing, Abdullah M. Asiri, Xuping Sun. NixSy-MoS2 hybrid microspheres: One-pot hydrothermal synthesis and their application as a novel hydrogen evolution reaction electrocatalyst with enhanced activity. Electrochimica Acta, 2014, 137: 504–510
[3] Zhengwei Xie, Ping He, Licheng Du, Faqin Dong, Ke Dai, Tinghong Zhang. Comparison of four nickel-based electrodes for hydrogen evolution reaction. Electrochimica Acta, 2013, 88: 390-394
[4] Ping He, Xiaofang Yi, Yongjun Ma, Wei Wang, Faqin Dong, Licheng Du, Hongtao Liu. Effect of Gd2O3 on the hydrogen evolution property of nickel-cobalt coatings electrodeposited on titanium substrate, Journal of Physics and Chemistry of Solids, 2011, 72: 1261-1264

Figure 1
First-Principles Study of Structure Property Relationships of Monolayer (Hydroxy)Oxide-Metal Bifunctional Electrocatalysts
Authors: Zeng Zhenhua , Kubal Joseph , Greeley Jeff 
Published: February 2020

In the present study, on the basis of detailed density functional theory (DFT) calculations, and using Ni hydroxy(oxide) films on Pt(111) and Au(111) electrodes as model systems, we describe a detailed structural and electrocatalytic analysis of hydrogen evolution (HER) at three-phase boundaries under alkaline electrochemical conditions. We demonstrate that the structure and oxidation state of the films can be systematically tuned by changing the applied electrode potential and/or the nature of substrates. Structural features determined from the theoretical calculations provide a wealth of information that is inaccessible by purely experimental means, and these structures, in turn, strongly suggest that a bifunctional reaction mechanism for alkaline HER will be operative at the interface between the films, the metal substrates, and the surrounding aqueous medium. This bifunctionality produces important changes in the calculated barriers of key elementary reaction steps, including water activation and dissociation, as compared to traditional monofunctional Pt surfaces.
The successful identification of the structures of thin metal films and three-phase boundary catalysts is not only an important step towards accurate identification and prediction of a variety of oxide/electrode interfacial structure-properties relationships, but also provides the foundation for rational design and control of ‘targeted active phases’ at catalytic interfaces. The successful design of bifunctional electrocatalysts that exploit these structures, in turn, could ultimately lead to advances in the development of alkaline fuel cells.
References

1Surnev, S.; Fortunelli, A.; Netzer, F. P. Chem Rev 2012, 113, 4314.

2Shaikhutdinov, S.; Freund, H.-J. Annu. Rev. Phys. Chem. 2012, 63, 619.

3Subbaraman, R.; Stamenkovic, V.; Markovic, N. et al, Science 2011, 334, 1256.

4Subbaraman, R.; Greeley, J.; Stamenkovic, V.; Markovic, N. et al, Nat Mater
2012, 11, 550

5Strmcnik, D; Stamenkovic, V. R.; Markovic, N. et al, Nat Chem 2013, 5, 300.
Materials for Efficient Photoelectrochemical Water Splitting: The PEC Working Group
Authors: Wang Heli , Jaramillo Thomas F , Miller Eric Lars 
Published: February 2020

The development of durable photoelectrochemical (PEC) water splitting systems with high solar-to-hydrogen (STH) conversion efficiency has been a significant challenge. Critical requirements on semiconductor materials’ band gap, energetics, efficiency, and stability must be satisfied simultaneously.
Metal oxides can be stable and earth-abundant, and different tandem cell configurations have been developed to address the band-edges mismatch. More focus is needed on overcoming the efficiency limitations due to absorption, charge mobility, recombination, interfacial kinetics, etc. With suitable band gaps and optoelectronic quality, high efficient PV semiconductors, like III-V, offer alternative pathway to efficient STH conversion by addressing the band edge mismatch using monolithic PEC/PV tandem cell design. Stability, however, remains a key issue. NREL, working with other members of the PEC working group have been investigating the corrosion of III-V materials and interfaces with a goal to develop surface modification methods for mitigating the corrosion issue. Approaches include coatings, ion bombardment, surface nitridation as well as electrolyte treatments.
Significant materials challenges remain, and effective usage of resources is needed. The PEC Working Group facilitates progress by bringing together diverse PEC researchers with common interests and goals, promoting collaborative activities, resource sharing, and joint publications.