Fast Oxygen Reduction Catalyzed by a Copper(II) Tris(2‐pyridylmethyl)amine Complex through a Stepwise Mechanism

Abstract Catalytic pathways for the reduction of dioxygen can either lead to the formation of water or peroxide as the reaction product. We demonstrate that the electrocatalytic reduction of O 2 by the pyridylalkylamine copper complex [Cu(tmpa)(L)] 2+ in a neutral aqueous solution follows a stepwise 4 e − /4 H + pathway, in which H 2 O 2 is formed as a detectable intermediate and subsequently reduced to H 2 O in two separate catalytic reactions. These homogeneous catalytic reactions are shown to be first order in catalyst. Coordination of O 2 to Cu I was found to be the rate‐determining step in the formation of the peroxide intermediate. Furthermore, electrochemical studies of the reaction kinetics revealed a high turnover frequency of 1.5×10 5 s −1 , the highest reported for any molecular copper catalyst.