Flexible Ligand in a Molecular Cu Electrocatalyst Unfurls Bidirectional O2/H2O Conversion in Water

The development of a bidirectional catalyst for oxygen reduction and water oxidation is the key to establishing sustainable energy transduction from renewable resources. We report a stable homogeneous molecular copper complex, comprising of a labile diimine-dioxime ligand framework, that enables rapid and complete 4e-/4H+ electrocatalysis for both oxygen reduction (2.1(±0.01) × 105 s-1) and water oxidation (3.2(±0.01) × 105 s-1) in aqueous solution presumably via in situ formation of binuclear intermediates. Computational investigations unravel the pivotal role of the interactive flexible ligand scaffold in accommodating the copper-core in variable oxidation states and influencing the O-O bond cleavage/formation dynamics during the catalysis. This study sets up a template for designing molecular catalysts for mediating energy-relevant multielectron/multiproton reactions in both oxidizing and reducing environments.