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

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2023-09, Vol.471, p.144490, Article 144490
• Main Authors: Navakoteswara Rao, Vempuluru, Kwon, Hyunguk, Lee, Yonghee, Ravi, Parnapalli, Won Ahn, Chi, Kim, Kyeounghak, Mo Yang, Jun
• Format: Article
• Language: English
• Subjects: DFT; Hierarchal structure; Mxene photocatalyst; Shell thickness; Stability; Valence state
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2023.144490

[Display omitted] •The Mxene nanosheets coupled with core–shell photocatalyst system by facile synthesis process.•The developed hierarchal nanostructures had a 16.2 mmol h−1 g-1cat photocatalytic H2 generation.•Optimized photocatalyst STH is 5.7 % and it showed remarkable stability in the long term.•The origin of the enhanced photocatalytic activity was elucidated by density functional theory (DFT) calculations. 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-1cat. 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