Ti₃C₂ Quantum Dots Modified 3D/2D TiO₂/g-C₃N₄ S-Scheme Heterostructures for Highly Efficient Photocatalytic Hydrogen Evolution

Photocatalytic hydrogen production is a promising technology to alleviate the problems of energy shortage and environmental pollution faced by human society. In this paper, the S-scheme heterojunction TiO2/g-C3N4 was modified by Ti3C2 quantum dots (QDs) to prepare a three-dimensional/two-dimensional/zero-dimensional (3D/2D/0D) photocatalyst for photocatalytic hydrogen production. The S-scheme heterojunction structure reduces the recombination rate of photogenerated electron–hole pairs and produces more photogenerated electrons. At the same time, Ti3C2 quantum dots as electron acceptors improve the ability to capture transition electrons, obtain more photogenerated carriers involved in surface reactions, and increase the number of active sites. The TiO2/g-C3N4/Ti3C2 QDs composite catalyst shows excellent photocatalytic hydrogen evolution performance under visible light due to its unique structure and optical properties. The photocatalytic hydrogen production rate reached the maxima of 5540.21 μmol·h–1 g–1, which is nearly 2 times higher than the production rates observed for TiO2/g-C3N4. The structure of 3D/2D/0D TiO2/g-C3N4/Ti3C2 QDs was constructed, and the electron transfer path was verified by transient absorption spectroscopy and density functional theory calculation.