Fabrication of the CdS-Cd₂Nb₂O₇ Nanocomposite Heterojunction with Cadmium Vacancy for Efficient Piezocatalytic H₂ Evolution

Piezocatalytic hydrogen evolution represents a promising strategy for generating sustainable energy. The construction of heterojunctions can realize the efficient separation and migration of charges and thus achieve enhanced H2 evolution performance. In this study, we report the fabrication of a CdS-Cd2Nb2O7 (CdS-CNO) heterojunction piezocatalyst with cadmium vacancies aimed at improving hydrogen evolution performance. Cadmium sulfide (CdS) was combined with cadmium niobate (Cd2Nb2O7, CNO) to form a heterojunction through a photodeposition strategy. By regulating the photodeposition time, CdS-CNO nanocomposites with varying CdS contents were successfully obtained. Cadmium vacancies were introduced into the CNO matrix during the photodeposition process, where cadmium ions within the CNO lattice reacted with sulfur ions to form CdS, resulting in the creation of cadmium vacancies. Experimental results demonstrated that the CdS-CNO-4 composite, with an optimized CdS content, exhibited the highest piezoelectric hydrogen production activity of 6.01 mmol·g–1·h–1, which is much higher than those of most previously reported piezocatalysts. The enhanced performance is attributed to the strong internal electric field generated by piezoelectric polarization and efficient charge carrier separation facilitated by the heterojunction and cadmium vacancies. This study aims to provide a strategy for developing highly efficient heterojunction piezocatalysts.