Selective facet stabilization of anatase TiO₂ by Sn doping

Anatase titanium dioxide (TiO₂) is widely recognized for its superior photocatalytic capabilities due to its indirect band gap, low cost, and high chemical stability compared to other oxide semiconductors. Despite its advantages, TiO₂ still suffers from intrinsic limitations, particularly rapid charge carrier recombination. To overcome these limitations, extensive research has focused on tailoring the surface structure of TiO₂, particularly through morphology engineering that optimizes facet exposure and improves reactivity. In terms of photocatalysis, two surfaces can be mainly considered in anatase TiO₂: (001) surface with notably high reactivity and (101) surface with lower reactivity; and thus the higher photocatalytic activity requires a higher proportion of the (001) surface, which contradicts to fact that the (001) and (101) surfaces have the surface energies of 0.90 J/m² and 0.44 J/m², respectively. We attempt Sn-doping to reduce the surface energy disparity and then stabilize the (001) surface. Our results demonstrate that Sn incorporation during growth stabilizes the (001) facet and promotes the formation of a (001)/(101) facet heterojunction. CL measurements further show suppressed radiative recombination relative to an undoped TiO₂ thin film. We provide insights into the approach for achieving facet-selective surface stabilization through Sn incorporation.