Determining the electrochemical activation mechanism of Prussian blue analog precatalysts for a high-efficiency oxygen evolution reaction

Prussian blue analogues (PBAs) are regarded as effective pre-catalysts for oxygen evolution reaction (OER), but the underlying mechanism of their electrochemical activation is still not well elucidated. In this work, we design and construct PBAs-based pre-catalysts to unveil the activation mechanism and achieve high-efficient OER. The PBAs undergo in situ electrochemical transformation to form the corresponding metal (oxy)hydroxides (M(O)OH) as the true OER catalyst. More importantly, the hexacyanoferrate ligands are unveiled to experience repetitive interfactial coordination/etching with/from the M(O)OH during the activation process. The distinct mechanism could achieve in situ Fe doping and the increase of defect concentration. The defect-enriched Fe-NiOOH derived from a well-designed NiHCF/Ni(OH)₂ pre-catalyst requires a low overpotential of 227 mV to drive the current density of 10 mA cm^-2, and could work stably at 130 mA cm^-2 over 100 h. This work offers a fundamental insight into the activation mechanism for developing advanced pre-catalysts for OER.