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Interface Controlled Oxidation States in Layered Cobalt Oxide Nanoislands on Gold

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Author

  • Alex S. Walton
  • Jakob Fester
  • Michal Bajdich
  • Mohammad A Arman
  • Jacek Osiecki
  • Jan Knudsen
  • Aleksandra Vojvodic
  • Jeppe V. Lauritsen

Summary, in English

Layered cobalt oxides have been shown to be highly active catalysts for the oxygen evolution reaction (OER; half of the catalytic "water splitting" reaction), particularly when promoted with gold. However, the surface chemistry of cobalt oxides and in particular the nature of the synergistic effect of gold contact are only understood on a rudimentary level, which at present prevents further exploration. We have synthesized a model system of flat, layered cobalt oxide nanoislands supported on a single crystal gold (111) substrate. By using a combination of atom-resolved scanning tunneling microscopy, X-ray photoelectron and absorption spectroscopies and density functional theory calculations, we provide a detailed analysis of the relationship between the atomic-scale structure of the nanoislands, Co oxidation states and substrate induced charge transfer effects in response to the synthesis oxygen pressure. We reveal that conversion from CO2+ to Co3+ can occur by a facile incorporation of oxygen at the interface between the nanoisland and gold, changing the islands from a Co-O bilayer to an O-Co-O trilayer. The O-Co-O trilayer islands have the structure of a single layer of beta-CoOOH, proposed to be the active phase for the OER, making this system a valuable model in understanding of the active sites for OER. The Co oxides adopt related island morphologies without significant structural reorganization, and our results directly demonstrate that nanosized Co oxide islands have a much higher structural flexibility than could be predicted from bulk properties. Furthermore, it is clear that the gold/nanoparticle interface has a profound effect on the structure of the nanoislands, suggesting a possible promotion mechanism.

Publishing year

2015

Language

English

Pages

2445-2453

Publication/Series

ACS Nano

Volume

9

Issue

3

Document type

Journal article

Publisher

The American Chemical Society (ACS)

Topic

  • Nano Technology

Keywords

  • water splitting
  • electrocatalysis
  • nanocatalysis
  • cobalt oxide
  • two-dimensional materials
  • reducible metal oxides

Status

Published

Project

  • Probing Atomic Scale Structure and Catalytic Properties of Cobalt Oxide Model Catalysts

ISBN/ISSN/Other

  • ISSN: 1936-086X