Electrochemical water oxidation by cobalt-Prussian blue coordination polymer and theoretical studies of the electronic structure of the active species.

The search for earth-abundant metal-based catalysts for the oxygen evolution reaction (OER) that operates under neutral conditions is a challenge in the field of sustainable energy. Many strategies have been used, and coordination polymers with structures similar to Prussian blue appear to be interesting electrocatalysts due to their efficiency, stability and tunable properties. In this paper, a novel catalyst produced from a cobalt-pentacyanidoferrate precursor is presented and applied in studies of the OER. This material showed a high surface active area and electrocatalytic activity comparable to traditional cobalt hexacyanidoferrate. According to the theoretical calculations, the improvement of these properties is an effect of the framework arrangement and it is not caused by changes of the electronic structure. Further experimental evidence is necessary to determine the active species. However, our results of spin densities obtained from DFT calculations suggest that the active species for water oxidation is the radical Fe(iii)-CN-Co(iii)-O˙.