Synergistic effect of dual phase cocatalysts: MoC-MoC quantum dots anchored on g-CN for high-stability photocatalytic hydrogen evolution.

The extensive examination of hexagonal molybdenum carbide (β-MoC) as a non-noble cocatalyst in the realm of photocatalytic H evolution is predominantly motivated by its exceptional capacity to adsorb H ions akin to Pt and its advantageous conductivity characteristics. However, the H evolution rate of photocatalysts modified with β-MoC 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-MoC decorated on g-CN (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 H, with a rate of 4078 µmol gh 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 H evolution rate of 40 mmol gh. The heightened level of activity observed in the 3-MC@C/gCN system can be ascribed to the synergistic effects of MoC-MoC 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-MoC@C composite served as active sites, thereby facilitating the H 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 H production.