Molecular Cluster Complex of High-Valence Chromium Selenide Carbonyl as Effective Electrocatalyst for Water Oxidation

Abstract

Developing simple, affordable, and environmentally friendly water oxidation electrocatalysts with high intrinsic activity and low overpotential continues to be an area of intense research. In this article, a trichromium diselenide carbonyl cluster complex (Et4N)2[Se2Cr3(CO)10], with a unique bonding structure comprising bridging Se groups, has been identified as a promising electrocatalyst for oxygen evolution reaction (OER). This carbonyl cluster exhibits a promising overpotential of 310 mV and a low Tafel slope of 82.0 mV dec−1 at 10 mAcm−2, with superior durability in an alkaline medium, for a prolonged period of continuous oxygen evolution. The mass activity and turnover frequency of 62.2 Ag−1 and 0.0174 s−1 was achieved, respectively at 0.390 V vs. RHE. The Cr-complex reported here shows distinctly different catalytic activity based on subtle changes in the ligand chemistry around the catalytically active Cr site. Such dependence further corroborates the critical influence of ligand coordination on the electron density distribution which further affects the electrochemical activation and catalytic efficiency of the active site. Specifically, even partial substitution with more electronegative substituents leads to the weakening of the catalytic efficiency. This report further demonstrates that metal carbonyl chalcogenides cluster-type materials which exhibit partially occupied sites and high valence in their metal sites can serve as catalytically active centers to catalyze OER exhibiting high intrinsic activity. The insight generated from this report can be directly extrapolated to 3-dimensional solids containing similar structural motifs, thereby aiding in optimal catalyst design.