Rational Design Rules for Molecular Water Oxidation Catalysts based on Scaling Relationships.

Lowering the overpotential required for water oxidation is of paramount importance for the efficient production of carbon-neutral fuels. This article highlights the intrinsic influence of the water oxidation mechanism used by molecular catalysts on the theoretically achievable minimal overpotential, based on scaling relationships typically used for heterogeneous catalysts. Due to such scaling relationships, catalysts that operate through the water nucleophilic attack mechanism have a fundamental minimal overpotential of about 0.3 V, whereas those that follow the dinuclear radical oxo coupling mechanism should in principle be able to operate with a lower overpotential. Therefore, it is recommended to design catalysts operating through the latter mechanism to achieve very efficient water oxidation systems.