In situ construction of an α-MoC/g-C3N4 Mott–Schottky heterojunction with high-speed electron transfer channel for efficient photocatalytic H2 evolution

Abstract

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 H₂ production reactions. However, the high synthetic temperature (≥700 °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 α-MoC nanodots with a diameter of 1.8 nm under 500 °C. Furthermore, α-MoC/g-C₃N₄ Mott–Schottky heterojunction was successfully constructed in situ for the first time, which delivers a 110-fold enhancement of H₂ 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 α-MoC, thus boosting photocatalytic H₂ 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.