Oxygen Vacancy-Induced Construction of CoO/h-TiO₂ Z-Scheme Heterostructures for Enhanced Photocatalytic Hydrogen Evolution

Abstract

Environmentally friendly catalysts with excellent performance and low cost are critical for photocatalysis. Herein, using hydrogenated TiO₂ (h-TiO₂) nanosheets with enriched oxygen vacancies as the support, two-dimensional CoO/h-TiO₂ Z-scheme heterostructures are fabricated for hydrogen production through photocatalytic water splitting. It is revealed that the oxygen vacancies in h-TiO₂ can inhibit the oxidation of Co²⁺ into high-valence Co³⁺ during the hydrothermal reaction and thermal treatment processes. A CoO/h-TiO₂ Z-scheme heterostructure possesses a space charge region and a built-in electric field at the interface, and oxygen vacancies in h-TiO₂ can provide more reactive sites, which synergistically improve the separation and transportation of photogenerated carriers. As a result, the photocatalytic hydrogen evolution rate achieves 129.75 μmol·h^-1 (with 50 mg of photocatalysts) on the optimized CoO/h-TiO₂ heterostructures. This work provides a new design idea for the preparation of excellent TiO₂-based photocatalysts.