Structure–Function Relationship of Surface Reconstruction in Cupric Oxide for Photochemical Sensing Properties

The anisotropy of surface structures in metal oxide-based semiconductor photocatalysts plays a critical role in governing photoactivated gas sensing properties. However, the surface reaction mechanism of the photochemical behavior remains poorly understood at the atomic scale. In this study, using CuO nanomaterials with various morphologies as a model system, including nanoparticles (NPs), nanorods (NRs), and nanosheets (NSs), we identified their surface atomic structures through aberration-corrected scanning transmission electron microscopy and first-principles calculation. We revealed the distinct surface reconstruction behaviors of the low Miller index surfaces. Photochemical sensing measurements showed that CuO NRs and CuO NSs, which predominantly expose oxygen-terminated (100) and copper-terminated (001) surfaces, respectively, exhibited optimized photoresponses toward H₂S and CH₃SH molecules. The concurrent adsorption of target molecules was revealed as the rate-determining step of the photocatalytic conversion. This work provides fundamental avenues for the predictive design and manipulation of surface reconstructions in metal oxides for a broad range of catalytic and sensing applications.