Bimetallic copper complexes for electrocatalytic bidirectional O2/H2O conversion in aqueous solution

Abstract

The distinctive interplay between abundant transition metal-containing active sites and their surrounding outer coordination sphere (OCS) is pivotal in achieving remarkable catalytic responses. In this context, copper complexes continue to garner attention as promising catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this article, we report two macrocyclic binuclear Cu complexes having variable peripheral functionalities around a common N2O2 like core. A mononuclear complex bearing the salophen-type ligand design was used as a control. The complex featuring peripheral OH groups demonstrates the highest catalytic activity in ORR (3050 s−1) and OER (6700 s−1), suggesting the crucial role of the alcoholic group during catalysis. In contrast, the mononuclear complex necessitates an additional thermodynamic stimulus to attain catalytic conditions for ORR and OER obverse to the case of binuclear complexes. Hence, this study establishes a template for designing molecular catalysts to mediate energy-relevant multielectron/multiproton reactions in both oxidizing and reducing environments.