An S-scheme Artificial Photosynthetic System with H-TiO2/g-C3N4 Heterojunction Coupled with MXene Boosts Solar H2 Evolution

Solar hydrogen production via water splitting is pivotal for solar energy harnessing, addressing key challenges in energy and environmental sustainability. However, two critical issues persist with single-component photocatalysts: suboptimal carrier transport and inadequate light absorption. While heterojunction-based artificial photosynthetic systems like Z-scheme photocatalysts have been explored, their charge recombination and light harvesting efficiency are still unsatisfactory. S-scheme heterojunctions have gained attention in photocatalysis, owing to their pronounced built-in electric field and superior redox capabilities. In this study, we introduce a MXene-based S-scheme H-TiO2/g-C3N4/Ti3C2 heterojunction (TCMX), synthesized through electrostatic self-assembly. The as-prepared TCMX exhibited an excellent photocatalytic hydrogen evolution rate of 53.67 mmol g−1 h−1 surpassing the performance of commercial Rutile TiO2, H-TiO2, g-C3N4, and HTCN. The effectiveness of TCMX is largely due to the built-in electric field in the S-scheme heterojunction and the cocatalytic activity of MXene promoting rapid separation of photogenerated charges and resulting in well-separated electron and hole enriched sites. This study offers a new approach to enhance photocatalytic hydrogen evolution efficiency and paves the way for the future design of S-scheme heterojunctions.