Synergistic integration of MXene nanosheets with CdS@TiO₂ core@shell S-scheme photocatalyst for augmented hydrogen generation

In order to ensure continuous and stable production of hydrogen (H₂), the development of hierarchical nanostructures within a few-layer Mxene nanosheet, incorporating an ultrathin TiO₂ shell material, is essential. This shell material plays a crucial role in maintaining the long-term stability of the core and preventing photo-corrosion, thus enabling uninterrupted H₂ generation. To evaluate their potential as visible-driven photocatalysts for high H₂ production, we conducted a comparative analysis of CdS cores covered with three different shell transition metal oxides (TiO₂@NiO@ZnO), supported by Mxene. Structural and morphological characterizations through XRD and TEM confirmed the formation of pure CdS@TiO₂@NiO@ZnO core–shell nanostructures, characterized by spherical shapes with a core diameter of 187 nm and a shell thickness of 19.2 nm. XPS experiments demonstrated the structural integrity of the individual elements within the nanocomposite, existing in their respective oxidation states within the core@shell structure. The hierarchical nanostructure exhibited optical characteristics with an absorption edge ranging from 480 to 580 nm. Among the three different shell materials, TiO₂ displayed the highest photocatalytic activity under visible light irradiation, followed by NiO and ZnO. Based on our findings, the CdS@TiO₂ core@shell photocatalyst supported by Mxene exhibited the highest efficiency, with a production rate of 16.2 mmol.h⁻¹.g^-1_cat. This can be attributed to enhanced charge separation, the spatial distribution of carriers, and favorable structural properties. Our DFT calculations further supported the efficacy of coupling Mxene with CdS/TiO₂, as it facilitated efficient water splitting, with CdS favoring H₂O dissociation and Mxene favoring HER. These results highlight the potential of developing highly efficient photocatalysts for water splitting by integrating Mxene with CdS/TiO₂. Additionally, The prepared CDTM (Mxene@CdS/TiO₂) photocatalyst existing S-scheme heterojunction for efficient water splitting. This underscores the system's effective functioning across diverse sceneries, Overall, our study presents a feasible and effective strategy for constructing an S-scheme heterojunction system that utilizes photo charge carrier separation to enhance the utilization and conversion of solar energy.