Effective photocatalytic hydrogen evolution by Ti3C2-modified CdS synergized with N-doped C-coated Cu2O in S-scheme heterojunctions

Photocatalytic hydrogen evolution through water splitting holds tremendous promise for converting solar energy into a clean and renewable fuel source. However, the efficiency of photocatalysis is often hindered by poor light absorption, insufficient charge separation, and slow reaction kinetics of the photocatalysts. In this study, we designed and synthesized a novel S-scheme heterojunction comprising Ti3C2 MXene, CdS nanorods, and nitrogen-doped carbon coated Cu2O (Cu2O@NC) core-shell nanoparticles. Ti3C2 MXene as a cocatalyst enhances the light absorption and charge transfer of CdS nanorods. Simultaneously, the core-shell Cu2O@NC nanoparticles establish a pathway for transferring photogenerated electrons and create a favorable band alignment for efficient hydrogen evolution. The synergistic effects of Ti3C2 MXene and Cu2O@NC on CdS nanorods result in multiple charge transfer channels and improved photocatalytic performance. The optimal hydrogen evolution rate of the Ti3C2-CdS-Cu2O@NC S-scheme heterojunction photocatalyst is 7.4 times higher than that of pure CdS. Experimental techniques and DFT calculations were employed to explore the structure, morphology, optical properties, charge dynamics, and band structure of the heterojunction. The results revealed that the S-scheme mechanism effectively suppresses the recombination of photogenerated carriers and facilitates the separation and migration of photogenerated electrons and holes to the reaction sites. Furthermore, Ti3C2 MXene provides abundant active sites essential for accelerating the surface H2-evolution reaction kinetics. The Cu2O@NC core-shell nanoparticles with a large surface area and high stability are closely adhered to CdS nanorods and establish an S-scheme internal electric field with CdS nanorods to drive charge separation. This investigation provides valuable insights into the rational design of CdS-based photocatalysts, enabling efficient hydrogen production by harnessing the robust kinetic driving force provided by the S-scheme heterojunctions.