Highly enhanced H2 evolution of MoO3/g-C3N4 hybrid composites based on a direct Z-scheme photocatalytic system

Abstract

The Z-scheme photocatalytic system has great potential in solar energy conservation with simultaneous wide light-absorption range, efficient electron–hole pair separation and strong redox ability. Herein, a direct Z-scheme g-C₃N₄/MoO₃ photocatalytic composite with oxygen vacancies is successfully fabricated via a facile in situ method of a one-pot pyrolysis strategy. The as-prepared g-C₃N₄/MoO₃ possesses a porous architecture with increased specific surface area. The existence of an oxygen vacancy in MoO₃ is verified by XPS, UV-DRS analysis and electrochemical measurements. The g-C₃N₄/MoO₃ exhibits superior visible-light photocatalytic performance for water splitting, as evidenced by an about 17-fold (20.52 μmol h⁻¹) increase in the rate of H₂ evolution relative to pristine C₃N₄ (1.23 μmol h⁻¹). According to the characterization results and boosted photocatalytic performance, the migration and separation of photoinduced charge carriers in g-C₃N₄/MoO₃ follows a possible mechanism based on a Z-scheme photocatalytic system constructed by the oxygen vacancies. The O-vacancy functions as the recombination and storage center for fast charge transfer through two components. The combined effect of defective MoO₃ and a Z-scheme interfacial heterojunction has achieved greatly enhanced photocatalytic performance. This work demonstrates the facilitation effect of an effective Z-scheme system involving oxygen vacancies on the charge transfer to enhance the photocatalytic activity for water splitting.