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Investigation of CoS2-based thin films as model catalysts for the oxygen reduction reaction

TitleInvestigation of CoS2-based thin films as model catalysts for the oxygen reduction reaction
Publication TypeJournal Article
Year of Publication2008
AuthorsZhu, L, Susac, D, Teo, M, Wong, KC, Wong, PC, Parsons, RR, Bizzotto, D, Mitchell, KAR, Campbell, SA
JournalJournal of Catalysis
Volume258
Pagination235-242
Date PublishedAug
Type of ArticleArticle
ISBN Number0021-9517
Keywordsatomic force microscopy, CO, CoS2, dynamic polarization, FUEL-CELLS, magnetron sputtering, micro-Raman spectroscopy, OXIDATION, oxygen reduction reaction, proton exchange membrane fuel cell, PYRITE SURFACES, RAMAN-SPECTROSCOPY, scanning Auger microscopy, SCATTERING, SPECTRA, SPECTROSCOPY, STATES, SULFUR, transition metal sulfide, X-RAY, x-ray diffraction, X-ray photoelectron
Abstract

Three CoS2-, NiS2- and (Co,Ni)S-2-based thin films were prepared by magnetron sputtering and studied as catalysts for the oxygen reduction reaction (ORR). Electrochemical assessments indicate that all three films have significant ORR catalytic activities, with that of (Co,Ni)S-2-type show ng the best performance with regard to both open circuit potential (OCP) and current density. The ternary film has an OCP value of 0.89 V vs. the reversible hydrogen electrode. and shows a closer approach to values for Pt than have been obtained to date for other transition metal chalcogenides. The thin films assessed by electrochemistry have been characterized by a range of techniques including high-resolution X-ray diffraction, micro-Raman spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy and scanning Auger microscopy. The CoS2-based film has a wrinkled surface, which appears relatively unchanged after an electrochemical durability test. while the NiS2-like film preferentially loses Ni and the (Co Ni)S-2-like, film (based on nanoparticles with approximate composition Co0.6Ni0.4S2) undergoes a phase separation. (spinodal decomposition). All these films show an excess of S in the as-prepared form and after electrochemistry; evidence is presented for the possible presence of some polysulfides. (c) 2008 Elsevier Inc. All rights reserved.

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