Pt–BiVO4/TiO2 composites as Z-scheme photocatalysts for hydrogen production from ethanol: the effect of BiVO4 and Pt on the photocatalytic efficiency

Abstract

A series of BiVO₄/TiO₂ nanocomposites with high surface area have been synthesized by a sol–gel method combined with supercritical drying. BiVO₄/TiO₂ samples with different BiVO₄ loadings were synthesized in order to study the effect of this variable on the structuration and development of BiVO₄/TiO₂ heterojunctions. Bare BiVO₄/TiO₂ composites are practically inactive for the photoproduction of hydrogen from ethanol under simulated solar light but their photoactivity notably improves after platinum (Pt) deposition. The photocatalytic activity of the Pt–BiVO₄/TiO₂ composites was determined by the BiVO₄/TiO₂ ratio that modifies the interfacial charge transfer efficiency between BiVO₄ and TiO₂ and also by the Pt loading that controls the dispersion and contact of the Pt particles with the composites. In particular, the composite with 0.5 wt% of Pt attained the optimal H₂ evolution rate, which is more than 100 times higher than that of the pristine BiVO₄/TiO₂ composite. The photoactivity of the Pt–BiVO₄/TiO₂ composites was explained according to the Z-scheme mechanism in which the electrons from the CB of TiO₂ reduced H⁺ to form H₂ through the Pt particles preferentially deposited on it.