A Cobalt(III) Corrole with a Tethered Imidazole for Boosted Electrocatalytic Oxygen Reduction Reaction

Developing electrocatalysts with high activity and selectivity for the oxygen reduction reaction (ORR) is vital to promote the performance of the next-generation energy technologies, which depend on the efficiency of the catalytic reduction of dioxygen. In the structure of cytochrome c oxidases (CcOs), a histidine imidazole residue binding to the axial position of Fe plays a crucial role in facilitating the selective reduction of O-2 to water. Inspired by nature, we herein report on the synthesis of Co-III corrole 1 tethered with an imidazole ligand as well as its electrocatalytic ORR and O-2 binding features. As compared to the imidazolium-free analogue, complex 1 displayed remarkably boosted activity for the selective four-electron/four-proton (4e(-)/4H(+)) ORR with a half-wave potential of E-1/2 = 0.82 V versus reversible hydrogen electrode (RHE) in 0.1 mol/L KOH solutions. Importantly, we demonstrate that the tethered axial imidazole ligand improves the O-2 binding ability of 1 thermodynamically and dynamically, which is crucial to boost electrocatalytic ORR performance. This work presents an example to improve electrocatalytic ORR activity and selectivity of Co corroles by introducing an axial imidazole ligand to enhance the O-2 binding and activation.