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Interface Controlled Oxidation States in Layered Cobalt Oxide Nanoislands on Gold

Walton, Alex S.; Fester, Jakob; Bajdich, Michal; Arman, Mohammad A LU ; Osiecki, Jacek LU ; Knudsen, Jan LU ; Vojvodic, Aleksandra and Lauritsen, Jeppe V. (2015) In ACS Nano 9(3). p.2445-2453
Abstract
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... (More)
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. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
water splitting, electrocatalysis, nanocatalysis, cobalt oxide, two-dimensional materials, reducible metal oxides
in
ACS Nano
volume
9
issue
3
pages
2445 - 2453
publisher
The American Chemical Society
external identifiers
  • wos:000351791800021
  • scopus:84925600186
ISSN
1936-086X
DOI
10.1021/acsnano.5b00158
language
English
LU publication?
yes
id
b430a5e6-b703-47f2-b78b-c6e9a9416ff1 (old id 5281426)
date added to LUP
2015-04-24 10:38:00
date last changed
2017-08-27 03:16:25
@article{b430a5e6-b703-47f2-b78b-c6e9a9416ff1,
  abstract     = {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.},
  author       = {Walton, Alex S. and Fester, Jakob and Bajdich, Michal and Arman, Mohammad A and Osiecki, Jacek and Knudsen, Jan and Vojvodic, Aleksandra and Lauritsen, Jeppe V.},
  issn         = {1936-086X},
  keyword      = {water splitting,electrocatalysis,nanocatalysis,cobalt oxide,two-dimensional materials,reducible metal oxides},
  language     = {eng},
  number       = {3},
  pages        = {2445--2453},
  publisher    = {The American Chemical Society},
  series       = {ACS Nano},
  title        = {Interface Controlled Oxidation States in Layered Cobalt Oxide Nanoislands on Gold},
  url          = {http://dx.doi.org/10.1021/acsnano.5b00158},
  volume       = {9},
  year         = {2015},
}