Facet-dependent photocatalytic performance and electronic structure of single-crystalline anatase TiO2 particles revealed by X-ray photoelectron spectromicroscopy†

Facet-tailored single-crystalline anatase TiO₂ particles with co-exposed (101)/(001) facets have been widely studied to enhance photocatalysis. Understanding the electronic structure of each facet is paramount for elucidating the charge separation mechanism and improving the photocatalytic performance. In this study, we used X-ray photoelectron spectromicroscopy with a spatial resolution of 100 nm to reveal the electronic structure of each facet of an anatase TiO₂ particle. The analysis revealed smaller core-level binding energies (O 1s and Ti 2p) and lower valence band maximum (VBM) for the (001) relative to the (101) facet of anatase. We also identified an interface structure where the VBM lies between the two facets. Our findings displayed a continuous band bending along the entire interface (∼181 nm) of the (101)/(001) facets as the VBM difference (ΔE = 0.65 eV). The interface serves as a convenient and rapid pathway for the vectorial transfer of photogenerated electrons and holes to the (101) and (001) facets, respectively, thereby offering significant benefits for heterogeneous catalysis applications. This study provides a deeper understanding of facet-dependent properties in anatase, paving the way for the design of more efficient photocatalysts tailored for specific environmental and energy-related applications.