BiVO4/CuIn5S8 heterojunction with rich sulphur vacancies for boosting visible light-driven photocatalytic water oxidation

The efficient conversion of water into clean energy using solar energy presents a sustainable solution to environmental challenges, albeit constrained by the slow kinetics of the oxygen evolution reaction. This study introduces a series of novel BiVO4/CuIn5S8 heterojunctions, developed and employed as photocatalysts for water oxidation. The photocatalytic activity of these heterojunctions was systematically enhanced by optimizing the BiVO4/CuIn5S8 ratio and hydrothermal reaction temperature. Notably, the heterojunction comprising BiVO4 coupled with 5 % CuIn5S8, synthesized at 180 °C (BiVO4/CuIn5S8/180–5), exhibited superior photocatalytic performance compared to its individual components. This enhancement was further augmented by the introduction of sulfur vacancies (VS) in VS-BiVO4/CuIn5S8/180–5, achieving approximately 3 and 1.4 times the photocatalytic activity of BiVO4 and BiVO4/CuIn5S8/180–5, respectively. Our findings demonstrate that CuIn5S8 effectively grows on decahedral BiVO4, forming n-n heterojunctions that not only improve visible light absorption but also facilitate the separation of photogenerated carriers. The incorporation of VS significantly lowers the charge carrier recombination rate and promotes the formation of additional active sites for H2O adsorption, thereby further elevating the efficiency of photocatalytic water oxidation.