title: Water Oxidation by Size-Selected Co27Clusters Supported on Fe2O3.
abstract: The complexity of the water oxidation reaction makes understanding the role of individual catalytic sites critical to improving the process. Here, size-selected 27-atom cobalt clusters (Co27) deposited on hematite (Fe2O3) anodes were tested for water oxidation activity. The uniformity of these anodes allows measurement of the activity of catalytic sites of well-defined nuclearity and known density. Grazing incidence X-ray absorption near-edge spectroscopy (GIXANES) characterization of the anodes before and after electrochemical cycling demonstrates that these Co27clusters are stable to dissolution even in the harsh water oxidation electrochemical environment. They are also stable under illumination at the equivalent of 0.4 suns irradiation. The clusters show turnover rates for water oxidation that are comparable or higher than those reported for Pd- and Co-based materials or for hematite. The support for the Co27clusters is Fe2O3grown by atomic layer deposition on a Si chip. We have chosen to deposit a Fe2O3layer that is only a few unit cells thick (2 nm), to remove complications related to exciton diffusion. We find that the electrocatalytic and the photoelectrocatalytic activity of the Co27/Fe2O3material is significantly improved when the samples are annealed (with the clusters already deposited). Given that the support is thin and that the cluster deposition density is equivalent to approximately 5 % of an atomic monolayer, we suggest that annealing may significantly improve the exciton diffusion from the support to the catalytic moiety.
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA. pellin@anl.gov.|Argonne-Northwestern Solar Energy Research (ANSER) Center, Argonne National Laboratory, Argonne, Illinois, 60439, USA. pellin@anl.gov.
authors.forename: Michael J
authors.identifier: http://orcid.org/0000-0002-8149-9768
authors.initials: MJ
authors.lastname: Pellin
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA.|Argonne-Northwestern Solar Energy Research (ANSER) Center, Argonne National Laboratory, Argonne, Illinois, 60439, USA.
authors.forename: Shannon C
authors.initials: SC
authors.lastname: Riha
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Tyo
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA.
authors.forename: Gihan
authors.initials: G
authors.lastname: Kwon
authors.affiliation: Energy Systems Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Libera
authors.affiliation: Energy Systems Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Elam
authors.affiliation: X-Ray Sciences Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA.
authors.forename: Soenke
authors.initials: S
authors.lastname: Seifert
authors.affiliation: X-Ray Sciences Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA.
authors.forename: Sungsik
authors.initials: S
authors.lastname: Lee
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA. vajda@anl.gov.|Nanoscience and Technology Division, Argonne National Laboratory, Argonne, Illinois, 60439, USA. vajda@anl.gov.|Department of Chemical and Environmental Engineering, Yale University, New Haven, CT, 06520, USA. vajda@anl.gov.|Institute for Molecular Engineering (IME), The University of Chicago, Chicago, IL, 60637, USA. vajda@anl.gov.
authors.forename: Stefan
authors.initials: S
authors.lastname: Vajda
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D014867:Water / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D014867:Water; C000499:ferric oxide; D003035:Cobalt
keywords: cobalt cluster; electrocatalysis; hematite; photoelectrocatalysis; water oxidation