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

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 (OV) defects in orthorhombic CaSnO3. Under an optimal SC CO2 pressure of 16 MPa, the treated CaSnO3 exhibits a partially amorphized surface, abundant OV, 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.