Operando SXRD/XAS studies of CoOx epitaxial thin films for OER electrocatalysis

Date: Sep 19, 2022
Time: 02:00 PM (Local Time Germany)
Speaker: Philippe Allongue
Directeur de Recherche at CNRS, Institut Polytechnique de Paris, 91128 Palaiseau, France.
Location: Building M, Richard-Willstätter-Haus, Faradayweg 10, 14195 Berlin
Room: Seminar Room
Host: Interface Science Department
Contact: roldan@fhi-berlin.mpg.de

Cobalt oxides are among the best earth abundant catalysts for the oxygen evolution reaction (OER) in alkaline and neutral electrolytes. We have undertaken operando studies of two dimensional epitaxial cobalt oxide films [1-2] to gain insights into some questions that remain in debate.

We use epitaxial CoOOH(001) and Co₃O₄(111) thin films (10-30 nm) with well-defined structure and morphology, which are grown by electrodeposition on Au (111). As operando characterizations, we used coupled surface x-ray diffraction (SXRD) / optical reflectivity and coupled operando SXRD / x-ray absorption spectroscopy (XAS). Recent data will be presented and it will be shown that they yield new insights into important questions such as the structure of the oxide surface in OER conditions, the number of atomic sites involved in the OER and the cobalt oxidation state (OS) at the surface in OER conditions.

[1] Finn Reikowski et al., Operando Surface X-ray Diffraction Studies of Structurally-defined Co3O4 and CoOOH Thin Films during Oxygen Evolution, ACS Catalysis, 9, 3811 (2019), https://doi.org/10.1021/acscatal.8b04823

[2] Tim Wiegmann et al., Operando identification of the reversible skin layer on Co3O4 as a three-dimensional reaction zone for oxygen evolution, ACS Catal., https://doi.org/10.1021/acscatal.1c05169