Construction of interfacial electric field via Bimetallic Mo2Ti2C3 QDs/g-C3N4 heterojunction achieves efficient photocatalytic hydrogen evolution

Exploiting photocatalysts with high interfacial charge separation efficiency remains a huge challenge for converting solar energy into chemical energy. Herein, a novel 0D/2D heterojunction is successfully constructed by using bimetallic Mo2Ti2C3 MXene Quantum Dots (Mo2Ti2C3 QDs) firmly immobilized on the surface of g-C3N4 nanosheet via an electrostatic self-assembly strategy. The Mo2Ti2C3 QDs/g-C3N4 exhibits an efficient and stable photocatalytic hydrogen production performance up to 2809 µmol g-1h-1, which is 7.96 times higher than pure g-C3N4 nanosheet, and prominently exceeding many reported photocatalysts. Besides, a prominent apparent quantum yield achieves 3.8% at 420 nm. The significant performance improvement derives from the giant interfacial electric field that formed between large interface contact areas, ensuring greatly efficient separation and transfer of the photogenerated carriers. Furthermore, the 0D/2D heterojunction possesses high-quality interfacial contact, which reduces the interfacial recombination of photoinduced electrons and holes, causing the quick electron transfer from the g-C3N4 to electron acceptor Mo2Ti2C3 QDs, thus enhancing the charge utilization. Kelvin probe force microscopy (KPFM) measurements and density functional theory (DFT) calculation comprehensively demonstrate that g-C3N4 modified by Mo2Ti2C3 QDs can modulate the electronic structure and prompt the establishment of the interfacial electric field, which consequently leads to efficient photocatalytic activity. This study adequately illustrates that constructing heterojunction interfacial electric fields based on MXene quantum dots is a prospective pathway to engineering high-performance photocatalytic platforms for solar energy conversion.