Mo x C Heterostructures as Efficient Cocatalysts in Robust Mo x C/g-C 3 N 4 Nanocomposites for Photocatalytic H 2 Production from Ethanol.

In this work, we studied new materials free of noble metals that are active in photocatalytic H 2 generation from ethanol aqueous solutions (EtOH aq ), which can be obtained from biomass. Mo x C/g-C 3 N 4 photocatalysts containing hexagonal (hcp) Mo 2 C and/or cubic (fcc) MoC nanoparticles on g-C 3 N 4 nanosheets were prepared, characterized, and evaluated for photocatalytic hydrogen production from EtOH aq (25% v/v). Tailored Mo x C/g-C 3 N 4 nanocomposites with Mo x C crystallite sizes in the 4-37 nm range were prepared by treatment with ultrasound of dispersions containing Mo x C and g-C 3 N 4 nanosheets, formerly synthesized. The characterization of the resulting nanocomposites, Mo x C/g-C 3 N 4 , by different techniques, including photoelectrochemical measurements, allowed us to relate the photocatalytic performance of materials with the characteristics of the Mo x C phase integrated onto g-C 3 N 4 . The samples containing smaller hcp Mo 2 C crystallites showed better photocatalytic performance. The most performant nanocomposite contained nanoparticles of both hcp Mo 2 C and fcc MoC and produced 27.9 mmol H 2 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-Mo 2 C heterojunctions. Moreover, this material allows for easy reusability. This work provides new insights for future research on noble-metal-free g-C 3 N 4 -based photocatalysts.