Electrochemical generation of unconventional cyanide vacancies to boost the catalytic performance of Co-Prussian Blue on oxygen evolution reaction under mild conditions

Abstract

The pursuit of cost-effective and environmentally abundant catalysts operating under mild conditions for water oxidation has directed focus toward Prussian blue analogues (PBAs), nonetheless, the low concentration of active sites still limits their high performance. Hence, here we report a straightforward electrochemical method to generate cyanide vacancies within a CoFePBA catalyst. The obtained material exhibited boosted catalytic performance associated with an enhancement of the available surface Co²⁺ sites. We report a 30% increase in the presence of CN^- defects, resulting in an estimated 32% enhancement in the catalytic activity. Finally, synchrotron-based soft X-ray spectroscopy assisted on the unraveling of key mechanistic insights and showed that the creation of defects can modulate the oxidation states within the material and favor the formation of Fe³⁺ -CN- Co²⁺ species, known to be more active. Therefore, this strategy can be presented as an efficient approach to enhance the number of active sites within earth-abundant catalysts.