TY - JOUR

T1 - Improved Hydrogen Oxidation Reaction Activity and Stability of Buried Metal-Oxide Electrocatalyst Interfaces

AU - Speck, Florian D.

AU - Ali, Farhan S.M.

AU - Paul, Michael T.Y.

AU - Singh, Ramesh K.

AU - Böhm, Thomas

AU - Hofer, André

AU - Kasian, Olga

AU - Thiele, Simon

AU - Bachmann, Julien

AU - Dekel, Dario R.

AU - Kallio, Tanja

AU - Cherevko, Serhiy

N1 - Funding Information: This work was funded within the project CREATE by the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 721065. The access to the Titan TEM was made possible through the School for Micro- and Nanostructure & Center for Nanoanalysis and Electron Microscopy (CENEM) at the Friedrich-Alexander-University (FAU) Erlangen-Nürnberg. This work was also partially funded by the Israel Science Foundation (ISF) [Grant No. 1481/17] and by the Planning & Budgeting Committee/ISRAEL Council for Higher Education (CHE) and Fuel Choice Initiative (Prime Minister Office of Israel), within the framework of “Israel National Research Center for Electrochemical Propulsion (INREP)”. We acknowledge funding by the German Ministry of Education and Research (BMBF) in the project “Tubulyze” (project number 03SF0564A). Publisher Copyright: Copyright © 2020 American Chemical Society. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/9/22

Y1 - 2020/9/22

N2 - Various bifunctional metal-oxide composites have recently been proposed as advanced hydrogen oxidation reaction (HOR) electrocatalysts for anion-exchange membrane fuel cells (AEMFCs). It is postulated that metal and oxide are active sites for the adsorption of hydrogen/proton and hydroxide ions, respectively. Of particular interest are the so-called buried interfaces. To investigate processes governing activity and stability at such interfaces, we prepare model Pd and Pt electrocatalysts which are fully covered by thin CeOx films. We investigate how oxide thickness influences HOR activity and dissolution stability of the electrocatalysts. It is found that materials behave very differently and that only Pd exhibits an enhanced HOR activity, while both oxide-protected metals are more stable toward dissolution. A 10-fold decrease in dissolution and 15-fold increase in HOR exchange current density are demonstrated for the optimized Pd/CeOx composites in comparison to pure Pd. We assess the mechanism of the electrocatalytic improvement as well as the role of the protective oxide films in such systems through advanced electrochemical and physical analysis. It is highlighted that a uniform, semipermeable oxide layer with a maximized electrocatalyst-oxide interface is crucial to form HOR catalysts with improved activity and stability.

AB - Various bifunctional metal-oxide composites have recently been proposed as advanced hydrogen oxidation reaction (HOR) electrocatalysts for anion-exchange membrane fuel cells (AEMFCs). It is postulated that metal and oxide are active sites for the adsorption of hydrogen/proton and hydroxide ions, respectively. Of particular interest are the so-called buried interfaces. To investigate processes governing activity and stability at such interfaces, we prepare model Pd and Pt electrocatalysts which are fully covered by thin CeOx films. We investigate how oxide thickness influences HOR activity and dissolution stability of the electrocatalysts. It is found that materials behave very differently and that only Pd exhibits an enhanced HOR activity, while both oxide-protected metals are more stable toward dissolution. A 10-fold decrease in dissolution and 15-fold increase in HOR exchange current density are demonstrated for the optimized Pd/CeOx composites in comparison to pure Pd. We assess the mechanism of the electrocatalytic improvement as well as the role of the protective oxide films in such systems through advanced electrochemical and physical analysis. It is highlighted that a uniform, semipermeable oxide layer with a maximized electrocatalyst-oxide interface is crucial to form HOR catalysts with improved activity and stability.

UR - http://www.scopus.com/inward/record.url?scp=85093069616&partnerID=8YFLogxK

U2 - 10.1021/acs.chemmater.0c02048

DO - 10.1021/acs.chemmater.0c02048

M3 - Article

AN - SCOPUS:85093069616

VL - 32

SP - 7716

EP - 7724

JO - Chemistry of Materials

JF - Chemistry of Materials

SN - 0897-4756

IS - 18

ER -