Delicate excavated trimetallic Prussian blue analogues for efficient oxygen evolution reactions

Highlights: • Prussian blue analogues (PBA) were delicately excavated by using sodium sulfide etching and subsequent annealing to PBA-SA. • This synthesized catalysts showed significant OER activity with a very low overpotential and a small Tafel slope. • The high performances are attributed to the synergistic effect, accelerated electrolyte diffusion and increased conductivity. -- Abstract: Efficiently modulating the pore size, electrochemical conductivity and metal ratio of metal-organic frameworks (MOFs) is essential for improving their electrochemical catalytic activity. Herein, we develop a convenient strategy for excavating Prussian blue analogues (PBA) by using sodium sulfide (Na₂S) as a delicate digger to modulate the pore size and metal ratio while maintaining the MOFs feature. A subsequent anneal at 300 °C removes cyanide groups and induces a collapse of the PBA structure that leads to an increase in the Fe valence and conductivity. These delicate excavated PBA catalysts exhibited high activity for the oxygen evolution reaction (OER) with a low overpotential of 261 mV at 10 mA cm⁻² and a small Tafel slope of 38 mV dec⁻¹, which exceeded that obtained for commercial IrO₂ in alkaline solution. This work may reveal a promising new method for exploring efficient MOFs-based electrocatalysts.