Concurrently Engineered Lewis Acid Sites and Coordination Sphere Vacancies in CoFe Prussian Blue Analogues for Boosted Bifunctional Oxygen Electrocatalysis

Prussian blue analogues (PBAs), due to their high surface area, large density of catalytically active sites, and high porosity, are one of the potential bifunctional oxygen electrocatalysts for industrial applications. However, so far, only limited success has been achieved toward developing highly efficient PBA-based electrocatalysts. Therefore, unravelling the underlying structure–property–activity relationship and designing strategies or combination of tested strategies are crucial to this effect. In this work, we demonstrate a strategy to concurrently engineer the coordination sphere vacancies and Lewis acid sites, via atomically dispersed Zn2+ dopants in CoFe PBA that makes Con+ more electropositive, to boost the bifunctional oxygen electrocatalysis on PBA surfaces. The optimal Zn-doping (3 mole %) not only enhances the oxygen evolution reaction (OER) activity of CoFe PBAs to the comparable level of the IrO2 catalyst but also depicts an impressive bifunctional oxygen activity with a low reversible overvoltage of 0.84 V. This work also demonstrates that an in situ formation of Co3+ (CoOOH) and Fe3+ (FeOOH) during the OER plays a crucial role for the boosted activity in bifunctional oxygen electrocatalysis. Besides providing highly efficient and low-cost catalysts, this study also imparts important insights to improve the efficiency of PBA-based bifunctional oxygen electrocatalysis.