Synergistic effect of dual phase cocatalysts: MoC-Mo₂C quantum dots anchored on g-C₃N₄ for high-stability...

The extensive examination of hexagonal molybdenum carbide (β-Mo₂C) as a non-noble cocatalyst in the realm of photocatalytic H₂ evolution is predominantly motivated by its exceptional capacity to adsorb H⁺ ions akin to Pt and its advantageous conductivity characteristics. However, the H₂ evolution rate of photocatalysts modified with β-Mo₂C is limited as a result of their comparatively low ability to release H through desorption. Therefore, a facile method was employed to synthesize carbon intercalated dual phase molybdenum carbide (MC@C) quantum dots (ca. 3.13 nm) containing both α-MoC and β-Mo₂C decorated on g-C₃N₄ (gCN). The synthesis process involved a simple and efficient combination of sonication-assisted self-assembly and calcination techniques. 3-MC@C/gCN exhibited the highest efficiency in generating H₂, with a rate of 4078 µmol g^-1h^-1 under 4 h simulated sunlight irradiation, which is 13 times higher than pristine gCN. Furthermore, from the cycle test, 3-MC@C/gCN showcased exceptional photochemical stability of 65 h, as it maintained a H₂ evolution rate of 40 mmol g^-1h^-1. The heightened level of activity observed in the 3-MC@C/gCN system can be ascribed to the synergistic effects of MoC-Mo₂C that arise due to the existence of a carbon layer. The presence of a carbon layer enhanced the transmission of photoinduced electrons, while the MoC-Mo₂C@C composite served as active sites, thereby facilitating the H₂ production reaction of gCN. The present study introduces a potentially paradigm-shifting concept pertaining to the exploration of novel Mo-based cocatalysts with the aim of augmenting the efficacy of photocatalytic H₂ production.