On the Homogeneity of a Cobalt-Based Water Oxidation Catalyst

Daan den Boer; Quentin Siberie; Maxime A Siegler; Thimo H Ferber; Dominik C Moritz; Jan P Hofmann; Dennis G H Hetterscheid

doi:10.1021/acscatal.2c01299

On the Homogeneity of a Cobalt-Based Water Oxidation Catalyst

ACS Catal. 2022 Apr 15;12(8):4597-4607. doi: 10.1021/acscatal.2c01299. Epub 2022 Apr 4.

Authors

Daan den Boer¹, Quentin Siberie¹, Maxime A Siegler², Thimo H Ferber³, Dominik C Moritz³, Jan P Hofmann³, Dennis G H Hetterscheid¹

Affiliations

¹ Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, RA, Leiden 2300, The Netherlands.
² Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore 21218 Maryland, United States.
³ Surface Science Laboratory, Department of Materials and Earth Sciences, Technical University of Darmstadt, Otto-Berndt-Strasse 3, Darmstadt 64287, Germany.

Abstract

The homogeneity of molecular Co-based water oxidation catalysts (WOCs) has been a subject of debate over the last 10 years as assumed various homogeneous Co-based WOCs were found to actually form CoO _x under operating conditions. The homogeneity of the Co(HL) (HL = N,N-bis(2,2'-bipyrid-6-yl)amine) system was investigated with cyclic voltammetry, electrochemical quartz crystal microbalance, and X-ray photoelectron spectroscopy. The obtained experimental results were compared with heterogeneous CoO _x . Although it is shown that Co(HL) interacts with the electrode during electrocatalysis, the formation of CoO _x was not observed. Instead, a molecular deposit of Co(HL) was found to be formed on the electrode surface. This study shows that deposition of catalytic material is not necessarily linked to the decomposition of homogeneous cobalt-based water oxidation catalysts.