Anion controlled selectivity in oxygen reduction catalysed by a dinuclear cobalt N,O-Schiff base complex

Abstract

A new dinuclear cobalt complex selectively catalyses 4e⁻ reduction of O₂ to water in methanol containing acetic acid. Its TOF of 0.031 s⁻¹ and overpotential of 690 mV outperform the few previous Co N,O-chelate based catalysts for the 4e⁻ ORR. Replacing acetic acid with NH₄PF₆ as proton source induces a complete and unprecedented switch to the H₂O₂ producing 2e⁻ pathway. Mechanistic studies suggest a peroxo intermediate for both pathways, with acetate coordination/decoordination determining the destination of a key electron transfer.