Supercritical CO₂-Modulated Surface Amorphization and O_V Defect in CaSnO₃ for High-Efficiency Electrocatalytic H₂O₂...

The electrochemical two electron water oxidation reaction (2e-WOR) offers a promising route for hydrogen peroxide (H₂O₂) production, but its efficiency is limited by the lack of high performance electrocatalysts. Herein, we report a supercritical carbon dioxide (SC CO₂) modulation strategy to synergistically engineer surface amorphization and oxygen vacancy (O_V) defects in orthorhombic CaSnO₃. Under an optimal SC CO₂ pressure of 16 MPa, the treated CaSnO₃ exhibits a partially amorphized surface, abundant O_V, and concomitant Sn³⁺ defects. These features collectively increase unsaturated coordination sites, accelerate interfacial charge transfer, and lower the reaction overpotential. Consequently, the optimal catalyst achieves a H₂O₂ 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 CaSnO₃, with stable operation for 24 h. This work demonstrates that SC CO₂ 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 H₂O₂ synthesis.