Less is more: Enhancement of photocatalytic activity of g-C3N4 nanosheets by site-selective atomic layer deposition of TiO2

Zero-dimensional/two-dimensional (0D/2D) TiO 2 /g-C 3 N 4 heterostructural photocatalysts were fabricated via ALD technique. TiO 2 nanoparticles were “site-selectively grown” on g-C 3 N 4 nanosheets and the surface modification induced band engineering of the composite photocatalysts. Thus, the redox properties of the photocatalysts were fine tuned. Under visible light , since only g-C 3 N 4 was excited, TiO 2 was acting as the electron transport channel in the optimized interfacial structures . They effectively suppressed the recombination and facilitated the transfer of photogenerated charges, improving the photocatalytic activity. When both the components were excited under UV–vis light, the dynamic equilibrium of the conduction band positions on these n–n type semiconductor heterojunctions led to the increased recombination rate of charges, decreasing the reactivity for H 2 evolution. However, the photocatalytic degradation of organic pollutants by these composite photocatalysts exhibited enhanced activities, resulting from the photogenerated holes on VB of TiO 2 which could promote oxidation of organic pollutants with strong oxidation potentials. Furthermore, TiO 2 /g-C 3 N 4 photocatalysts with limited numbers of deposition cycles exhibited optimal photocatalytic activity under visible light. In contrast, excessive deposition cycles on g-C 3 N 4 for TiO 2 /g-C 3 N 4 led to continuous film and increased thickness of TiO 2 , resulting in the attenuation of the reactivity. We verified this TiO 2 /g-C 3 N 4 photocatalysts with less mass-loading, but more enhanced photocatalytic activity.