Supercritical CO ₂ ‐Modulated Surface Amorphization and O _V Defect in CaSnO ₃ for High‐Efficiency Electrocatalytic H ₂ O ₂ Production

ABSTRACT The electrochemical two electron water oxidation reaction (2e‐WOR) offers a promising route for hydrogen peroxide (H 2 O 2 ) production, but its efficiency is limited by the lack of high performance electrocatalysts. Herein, we report a supercritical carbon dioxide (SC CO 2 ) modulation strategy to synergistically engineer surface amorphization and oxygen vacancy (O V ) defects in orthorhombic CaSnO 3 . Under an optimal SC CO 2 pressure of 16 MPa, the treated CaSnO 3 exhibits a partially amorphized surface, abundant O V , and concomitant Sn 3+ defects. These features collectively increase unsaturated coordination sites, accelerate interfacial charge transfer, and lower the reaction overpotential. Consequently, the optimal catalyst achieves a H 2 O 2 production rate of 26.6 µmol cm− 2 min −1 , a Faradaic efficiency (FE) of 82% at 2.9 V versus RHE, and a cumulative yield over 300 min approximately eight times that of pristine CaSnO 3 , with stable operation for 24 h. This work demonstrates that SC CO 2 treatment is an effective tool to construct defect coupled surface amorphous regions, providing a new paradigm for designing high ‐ performance 2e‐WOR electrocatalysts for green H 2 O 2 synthesis.