In Situ Charge Modification within Prussian Blue Analogue Nanocubes by Plasma for Oxygen Evolution Catalysis

A targeted defect-induced strategy of metal sites in a porous framework is an efficient avenue to improve the performance of a catalyst. However, achieving such an activation without destroying the ordered framework is a major challenge. Herein, a dielectric barrier discharge plasma can etch the Fe(CN)₆ group of the NiFe Prussian blue analogue framework in situ through reactive oxygen species generated in the air. Density functional theory calculations prove that the changed local electronic structure and coordination environment of Fe sites can significantly improve oxygen evolution reaction catalytic properties. The modified NiFe Prussian blue analogue is featured for only 316 mV at a high current density (100 mA cm^-2), which is comparable to that of commercial alkaline catalysts. In a solar cell-driven alkaline electrolyzer, the overall electrolysis efficiency is up to 64% under real operation conditions. Over 80 h long-time continuous test under 100 mA cm^-2 highlights superior durability. The density functional theory calculations confirm that the formation of OOH* is the rate-determining step over Fe sites, and Fe(CN)₆ vacancy and extra oxygen atoms can introduce charge redistribution to the catalyst surface, which finally enhances the oxygen evolution reaction catalytic properties by reducing the overpotential by 0.10 V. Both experimental and theoretical results suggest that plasma treatment strategy is useful for modifying the skeletal material nondestructively at room temperature, which opens up a broad prospect in the field of catalyst production.