Construction of interfacial electric field via Bimetallic MoTiC QDs/g-CN 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 MoTiC MXene Quantum Dots (MoTiC QDs) firmly immobilized on the surface of g-CN nanosheet via an electrostatic self-assembly strategy. The MoTiC QDs/g-CN exhibits an efficient and stable photocatalytic hydrogen production performance up to 2809 µmol gh, which is 7.96 times higher than pure g-CN 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-CN to electron acceptor MoTiC QDs, thus enhancing the charge utilization. Kelvin probe force microscopy (KPFM) measurements and density functional theory (DFT) calculation comprehensively demonstrate that g-CN modified by MoTiC 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.