Sustainable carbon-based photocatalysts for solar H₂ production by photoreforming of plastic materials

Photocatalytic hydrogen production is among the top ten emerging technologies in chemistry. In particular, the photoreforming (PR) of organic substrates is an attractive way to obtain green H₂ together with the valorisation of waste or biomass. This reaction combines water reduction with the oxidation of a sacrificial agent using a semiconductor. In this context, it is possible to use, as sacrificial agents, new emerging water pollutants as plastic materials like polystyrene (PS) and polyethylene (PE) to obtain H₂ with a contextual water purification. Furthermore, an important point is the choice of photocatalysts. Carbon-based materials are prospective candidates for their remarkable electrical, thermal, and mechanical properties. For this reason, the focus of this work was to study the performance of composites based on metal carbides (MCs) (SiC, MoC, TiC) with different amounts of graphitic carbon nitride (g-C₃N₄). For the preparation of these catalysts, thermal polymerization was used, whereas for increasing the production of H₂, Pt (1 wt%) was added with wetness impregnation. The photocatalytic tests were performed with 50 mg of the photocatalyst, homogeneously suspended in an aqueous solution containing previously pre-treated PS or PE, with the photoreactor irradiated for 5 h using a solar lamp. A good production of H₂ was verified from all the investigated sacrificial agents. PE PR using the TiC1%g-C₃N₄_Pt sample allowed more H₂ (750 umol H₂/(gcat*h)) to be produced compared to PS PR (170umol H₂/(gcat*h)). This can be due to the easier C–C bond cleavage and C–C bond coupling of PE with respect to PS during the pre-treatment and the photoreforming reaction. The results obtained in this work pave the way for future environmental perspectives in which the pollutants can be considered new raw materials to obtain H₂, contextually preserving the water by the emerging contaminants.