MoC Heterostructures as Efficient Cocatalysts in Robust MoC/g-C₃N₄ Nanocomposites for Photocatalytic H₂ Production...

In this work, we studied new materials free of noble metals that are active in photocatalytic H₂ generation from ethanol aqueous solutions (EtOH_aq), which can be obtained from biomass. MoC/g-C₃N₄ photocatalysts containing hexagonal (hcp) Mo₂C and/or cubic (fcc) MoC nanoparticles on g-C₃N₄ nanosheets were prepared, characterized, and evaluated for photocatalytic hydrogen production from EtOH_aq (25% v/v). Tailored MoC/g-C₃N₄ nanocomposites with MoC crystallite sizes in the 4-37 nm range were prepared by treatment with ultrasound of dispersions containing MoC and g-C₃N₄ nanosheets, formerly synthesized. The characterization of the resulting nanocomposites, MoC/g-C₃N₄, by different techniques, including photoelectrochemical measurements, allowed us to relate the photocatalytic performance of materials with the characteristics of the MoC phase integrated onto g-C₃N₄. The samples containing smaller hcp Mo₂C crystallites showed better photocatalytic performance. The most performant nanocomposite contained nanoparticles of both hcp Mo₂C and fcc MoC and produced 27.9 mmol H₂ g^-1 Mo; this sample showed the lowest recombination of photogenerated charges, the highest photocurrent response, and the lowest electron transfer resistance, which can be related to the presence of MoC-Mo₂C heterojunctions. Moreover, this material allows for easy reusability. This work provides new insights for future research on noble-metal-free g-C₃N₄-based photocatalysts.