Lowering the Water Oxidation Overpotential by Spin-Crossover in Cobalt Hexacyanoferrate

The oxygen evolution reaction (OER) is limited by the inherent linearscaling relationships of its reaction intermediates. Manipulating the spin configuration ofthe water oxidation intermediates allows us to overcome these constraints. Cobalthexacyanoferrate (CoFe-PB) is an efficient and robust water oxidation catalyst andfurther known as a magnetic switch. Its versatile electronic structure renders it a potentialcandidate for magnetic tuning of the OER. Herein, we usedfirst-principles densityfunctional theory calculations to describe the OER on two different CoFe-PB modelsystems and evaluated the possibility for spin-crossover (SCO) of their resting states. Weshow that SCO during OER can significantly lower the overpotential by 0.7 V, leading toan overpotential of around 0.3 V, which is in agreement with the experimentallymeasured value. Applying an external potential >1.5 V vs SHE, the SCO-assisted pathwaybecomes largely favored and most likely the predominant reaction pathway