Boosting photocatalytic activity of CdLa2S4/ZnIn2S4 S-scheme heterojunctions with spatial separation of photoexcited carries

Abstract

Rational design and interfacial tuning of two-dimensional semiconductor S-scheme heterojunctions remain challenging to explore efficient photocatalysts in solar hydrogen production and treatment of organic pollution in water. In this study, the CdLa2S4/ZnIn2S4 S-scheme heterojunctions with flower-shaped ZnIn2S4 loaded with fishbone-like CdLa2S4 nano-bulks were synthesized based on the different work functions. The heterogeneous interface provides a large surface contact area between the catalyst and the reaction solution, maximizing the utilization of active sites on ZnIn2S4. By meticulous design from the structure and interface function perspective, the prepared CdLa2S4/ZnIn2S4 photocatalyst heterojunction exhibited excellent performance in hydrogen production and organic pollutant degradation. In particular, the optimal hydrogen production rate of CdLa2S4/ZnIn2S4 heterojunction was up to 1582.3 μmol·g−1·h−1 under light irradiation, which was 2.65 and 89.4 times higher than that of pristine ZnIn2S4 and CdLa2S4, respectively. Besides, the optimized composites achieved 98.9% and 74.1% degradation efficiency for photocatalytic degradation of SMZ and 2,4-DCP, respectively. The deep electron transfer mechanism of S-scheme heterojunction photocatalysts is revealed by characterization techniques and DFT theoretical calculations. Moreover, theoretical calculations reveal that the In surface in ZnIn2S4 can form a substantial interfacial coupling effect by contacting CdLa2S4. The carriers reverse their motion by being driven by the Fermi energy level difference at the interface and the built-in electric field. This work contributes to the extension of providing further insights and perspectives on the preparation of ZnIn2S4-based heterojunction photocatalysts.