title: Photoelectron Spectroscopy at the Graphene-Liquid Interface Reveals the Electronic Structure of an Electrodeposited Cobalt/Graphene Electrocatalyst.
abstract: Electrochemically grown cobalt on graphene exhibits exceptional performance as a catalyst for the oxygen evolution reaction (OER) and provides the possibility of controlling the morphology and the chemical properties during deposition. However, the detailed atomic structure of this hybrid material is not well understood. To elucidate the Co/graphene electronic structure, we have developed a flow cell closed by a graphene membrane that provides electronic and chemical information on the active surfaces under atmospheric pressure and in the presence of liquids by means of X-ray photoelectron spectroscopy (XPS). We found that cobalt is anchored on graphene via carbonyl-like species, namely Co(CO)x , promoting the reduction of Co(3+) to Co(2+), which is believed to be the active site of the catalyst.
authors.affiliation: Max Planck Institute for Chemical Energy Conversion, Mülheim 45470 (Germany). velasco@fhi-berlin.mpg.de.|Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin 14195 (Germany). velasco@fhi-berlin.mpg.de.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Velasco-Velez
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin 14195 (Germany).
authors.forename: Verena
authors.initials: V
authors.lastname: Pfeifer
authors.affiliation: Max Planck Institute for Chemical Energy Conversion, Mülheim 45470 (Germany).|Helmholtz-Center Berlin for Materials and Energy, BESSY II, Berlin 12489 (Germany).
authors.forename: Michael
authors.initials: M
authors.lastname: Hävecker
authors.affiliation: Engineering Department, University of Cambridge, Cambridge CB3 0FA (UK).|Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley 94720 (USA).
authors.forename: Robert S
authors.initials: RS
authors.lastname: Weatherup
authors.affiliation: Diamond Light Source, Oxfordshire OX11 0QX (UK).
authors.forename: Rosa
authors.initials: R
authors.lastname: Arrigo
authors.affiliation: Department of Physics, Tamkang University, Tamsui 251 (Taiwan).
authors.forename: Cheng-Hao
authors.initials: CH
authors.lastname: Chuang
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin 14195 (Germany).
authors.forename: Eugen
authors.initials: E
authors.lastname: Stotz
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin 14195 (Germany).
authors.forename: Gisela
authors.initials: G
authors.lastname: Weinberg
authors.affiliation: Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley 94720 (USA).
authors.forename: Miquel
authors.initials: M
authors.lastname: Salmeron
authors.affiliation: Max Planck Institute for Chemical Energy Conversion, Mülheim 45470 (Germany).|Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin 14195 (Germany).
authors.forename: Robert
authors.initials: R
authors.lastname: Schlögl
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin 14195 (Germany).
authors.forename: Axel
authors.initials: A
authors.lastname: Knop-Gericke
keywords: X-ray absorption spectroscopy; electrocatalysis; electrodeposition; graphene/cobalt; photoelectron spectroscopy