Enhanced charge transfer and separation of hierarchical hydrogenated TiO2 nanothorns/carbon nanofibers composites decorated by NiS quantum dots for remarkable photocatalytic H2 production activity

Abstract

Hierarchical core/shell hydrogenated TiO₂ (H-TiO₂) nanothorns/carbon nanofibers (CNFs) composites were produced through a solvothermal method, followed by ordinal calcination and hydrogenation treatments using the prepared carbon nanofiber as electron-transporting substrate material. The hierarchical H-TiO₂/CNFs composites possess more exposed surface active sites and offer efficient charge transport paths. NiS quantum dots as excellent electron acceptors and cocatalysts were anchored on the hierarchical H-TiO₂/CNFs composites by a wet chemical deposition method. The synergistic effects of the surface defects (oxygen vacancies), NiS cocatalyst, and carbon nanofibers greatly improve charge transfer and separation, increase the accessible surface area and surface donor density of the composites and also extend the photoresponse from the ultraviolet to the visible light region. By taking advantage of these features and because of its unique architecture, the optimal NiS quantum dots-decorated H-TiO₂/CNFs composite exhibited a remarkable solar-driven hydrogen generation rate (75.92 μmol h⁻¹, 30 mg⁻¹) in the absence of a Pt cocatalyst under AM 1.5 irradiation, which is about 12.3 times that of TiO₂/CNFs nanostructures.