Integrating CaIn2S4 nanosheets with Co3O4 nanoparticles possessing semiconducting and electrocatalytic properties for efficient photocatalytic H2 production

Abstract

A well-designed photocatalytic system needs to have broad light absorption, efficient charge separation and transfer kinetics, and excellent photostability. However, achieving these characteristics with a single photocatalyst is challenging. In this study, we propose coupling CaIn2S4 nanosheets with narrow band gap Co3O4 nanoparticles, which possess semiconducting and electrocatalytic properties, to form a Type II heterojunction with strong built-in electric field and high surface catalytic activity. We employs a two-step hydrothermal reaction to obtain the Co3O4/CaIn2S4 composite. The composite material displays an average rate of H2 evolution of 457.0 μmol g−1·h−1, which is 32.2 times higher than the rate achieved using pure CaIn2S4. Additionally, the composite photocatalyst demonstrates minimal decline in H2 production in five consecutive cycles. Our mechanism investigation reveals that Co3O4 can act as a semiconductor, forming a Type II heterojunction with CaIn2S4 producing an efficient photoelectron transfer channel from the conduction band of CaIn2S4 to Co3O4. Simultaneously, Co3O4 effectively transfers the separated electrons into the aqueous solution, functioning as a promising cocatalyst with low H-adsorption Gibbs free energy, thus enhancing the H2 production performance. This study highlights the importance of properly aligning energy levels and surface catalysis acceleration in the rational design of novel photocatalytic composites.