In situ topotactic formation of 2D/2D direct Z-scheme Cu2S/Zn0.67Cd0.33S in-plane intergrowth nanosheet heterojunctions for enhanced photocatalytic hydrogen production

Abstract

Zinc cadmium sulfide solid solution (Zn_xCd_1−xS) photocatalysts have received significant attention in energy and environmental applications because of their wide and strong visible light absorption range. However, the high photogenerated electron–hole pair recombination rate is an innate problem for their application. In this study, Cu₂S/Zn_0.67Cd_0.33S (CZCS) nanosheet heterojunctions were fabricated by the in situ topotactic hydrothermal transformation of CuZnCdAl layered double hydroxide (LDH) precursors. Structural and morphological characterization indicated that the CZCS nanosheets were 2D/2D atomic-level in-plane heterojunctions with matched crystalline orientation because of their intergrowth structure originating from the topotactic sulfurization of CuZnCdAl LDH precursors. This in-plane intergrowth structure enhanced the separation of photogenerated electron–hole pairs based on a direct Z-scheme mechanism, which, in addition to providing a wide light absorption range and appropriate flat band potential, endowed excellent photocatalytic hydrogen production at the rate of 15.27 mmol h⁻¹ g⁻¹ (about 3.82 times that of pure Zn_0.67Cd_0.33S) from water splitting under visible light irradiation without the additive Pt cocatalysts. This photocatalyst with a superior photocatalytic activity and cycling stability can serve as a hopeful candidate for applications in the energy and environment field.