Self-assembled nanohybrid of cadmium sulfide and calcium niobate: Photocatalyst with enhanced charge separation for efficient visible light induced hydrogen generation

A nanohybrid of CdS and HCa₂Nb₃O₁₀ with enhanced separation of charge carriers was conveniently prepared by self-assembly of negatively charged HCa₂Nb₃O₁₀ nanosheets with the existence of Cd²⁺ followed by sulfuration. With CdS working as a visible light absorbent, HCa₂Nb₃O₁₀, with a wide bandgap, showed H₂ evolution activity without cocatalysts upon visible light excitation and neutral pH (450 μmol h⁻¹ g_cat ⁻¹), and showed a high quantum efficiency of 7.2% at 425 nm because of enhanced charge separation. The self-assembly method rapidly realized introduction of guest materials into the interlayer space of layered perovskites from a layer-by-layer strategy, showing great potential in synthesizing novel 2D material based hybrid photocatalyst. A type II composite band structure was obtained from combination of CdS and niobates, making it possible for spontaneous charge separation. While ultra-fine nature of the guest CdS, ultra-thin nature of the host niobate nanosheets and close junction between the host and guest components facilitated charge transfer between components. Enhanced charge separation in hybrid photocatalyst is the key factor that leads to its superior photocatalytic performance in comparison with its components. This work extends photocatalytic application of wide gap niobates into visible light region. Since the unique nanostrucute and charged nature of 2D materials can be fully utilized, it is believable that more efficient photocatalytic water splitting can be realized by constructing nanosheets based hybrids in the future.