Single‐Site Copper(II) Water Oxidation Electrocatalysis: Rate Enhancements with HPO 4 2− as a Proton Acceptor at pH 8

The complex Cu II (Py 3 P) ( 1 ) is an electrocatalyst for water oxidation to dioxygen in H 2 PO 4 − /HPO 4 2− buffered aqueous solutions. Controlled potential electrolysis experiments with 1 at pH 8.0 at an applied potential of 1.40 V versus the normal hydrogen electrode resulted in the formation of dioxygen (84 % Faradaic yield) through multiple catalyst turnovers with minimal catalyst deactivation. The results of an electrochemical kinetics study point to a single‐site mechanism for water oxidation catalysis with involvement of phosphate buffer anions either through atom–proton transfer in a rate‐limiting OO bond‐forming step with HPO 4 2− as the acceptor base or by concerted electron–proton transfer with electron transfer to the electrode and proton transfer to the HPO 4 2− base.