Defect‐Rich CoNi Prussian Blue Analogues Enable Highly Selective Electrochemical Hydrogen Peroxide Production

Decentralized electrosynthesis of hydrogen peroxide (H 2 O 2 ) via the two‐electron oxygen reduction reaction (2e − ORR) offers a promising alternative to the traditional anthraquinone process, though developing non‐precious metal electrocatalysts with high activity, selectivity, and industrial durability remains challenging. Herein, we report a defect‐engineering strategy to synthesize CoNi Prussian blue analogues (PBAs) with precisely tunable [Co(CN) 6 ] 3− vacancy concentrations via kinetic trapping. Advanced synchrotron X‐ray diffraction and absorption spectroscopy (EXAFS) reveal that these vacancies transform the local coordination of adjacent nickel atoms from saturated octahedral geometries to unsaturated square‐planar Ni–N 4 motifs. This structural modulation triggers a fundamental shift in the ORR pathway, delivering an H 2 O 2 selectivity exceeding 97% and a remarkable production rate of 6.2 in a flow‐cell device. Crucially, our defect‐rich catalyst demonstrates exceptional durability under a rigorous 120‐h variable‐current stability test. Density functional theory (DFT) calculations identify the coordinatively unsaturated Ni–N 4 sites as the intrinsic active centers, which optimize the binding energy of the *OOH intermediate and suppress the four‐electron ORR pathway. This work identifies a robust H 2 O 2 synthesis electrocatalyst and establishes a validated protocol for defect engineering in coordination frameworks.