In situ construction of an alpha-MoC/g-C3N4 Mott-Schottky heterojunction with high-speed electron transfer channel for efficient photocatalytic H-2 evolution

The design and construction of the Mott-Schottky heterojunction with the superior separation and transfer efficiency of photogenerated carriers are significant for solar-to-hydrogen conversion. Molybdenum carbide has been regarded as a promising cocatalyst for replacing Pt in photocatalytic H-2 production reactions. However, the high synthetic temperature (>= 700 degrees C) is not beneficial for the achievement of molybdenum carbide with a small size and the construction of an intimate heterojunction with semiconductor photocatalysts, leading to inferior photocatalytic performance and stability. Herein, we developed an organic-inorganic hybrid strategy to achieve the low-temperature synthesis of ultra-small alpha-MoC nanodots with a diameter of 1.8 nm under 500 degrees C. Furthermore, alpha-MoC/g-C3N4 Mott-Schottky heterojunction was successfully constructed in situ for the first time, which delivers a 110-fold enhancement of H-2 production compared to bare g-C3N4. The experimental results and density functional theory (DFT) calculations revealed that intimate contact through the Mo-N bond is a feasible method to decrease the Schottky barrier and facilitate electron transfer from g-C3N4 to alpha-MoC, thus boosting photocatalytic H-2 evolution performance. This study provides a mild strategy for the synthesis of ultra-small molybdenum carbide nanoparticles and highlights the great potential of the Mott-Schottky heterojunction with a high-speed electron transfer channel for efficient solar energy-driven conversion.