Defect and Interface Co-Regulation Enabled Piezoelectricity Activation in SnSe₂ for High-Performance Piezo-Photocatalytic H₂O₂ Generation and Uranium Extraction

The centrosymmetric crystal structure of SnSe₂ intrinsically excludes a piezoelectric property. Herein, a piezoelectric effect of SnSe₂ is activated via introducing Se vacancies (SnSe₂-V_Se), endowing a piezoelectric coefficient as high as 19.9 pm V⁻¹. By leveraging the continuous anionic framework, the valence state compatibility, and the comparable atomic radii between Se and S, an atomically precise S-scheme SnSe₂-V_Se@In₂S₃ heterojunction is constructed. Systematic studies demonstrate that the Se vacancies generate strong localized polarization fields, which, in conjunction with the interfacial built-in electric field (IEF) in SnSe₂-V_Se@In₂S₃, significantly enhance the carrier separation efficiency by 16-fold as compared to pristine SnSe₂-V_Se. Theoretical calculations reveal that interfacial electronic coupling facilitates O₂ adsorption, while an upward shift in the Sn d-band center optimizes the adsorption free energy of ^*OOH intermediates. Under the piezo-photocatalysis, the system achieves an H₂O₂ generation rate of 2.38 mmol g⁻¹ h⁻¹ through the oxygen reduction pathway, alongside enhanced O₂ evolution via water oxidation. Further, in-situ generated H₂O₂ mediates efficient U(VI) reduction and precipitation, enabling almost 100% uranium extraction from both simulated wastewater and artificial seawater.