RuO₂/g-C₃N₄ catalysts for efficient light-driven hydrogen evolution

The evolution of the photocatalysis field relies heavily on the development of materials with higher efficiency and long-term stability. Graphitic carbon nitride (g-C₃N₄, here denoted as GCN) is a robust photocatalyst known for its high stability and low preparation cost using readily available raw materials. Combining GCN with co-catalysts, such as metal oxides, is known to be an efficient strategy for enhancing photocatalytic activity by improving charge-transfer dynamics. In this work, RuO₂/GCN materials containing different RuO₂ contents (xRuO₂/GCN; x = 0.2 – 5.0 wt.%) were synthesised and tested for photocatalytic hydrogen (H₂) evolution. GCN was produced by thermal polymerisation of dicyandiamide. Hybrid materials were prepared by wet impregnation, in which GCN was added to a dispersion of the desired amount of RuO₂ precursor (RuCl3) in water at 70 °C, until partial solvent evaporation. After washing and drying, the materials were calcinated at 400 °C. Photocatalytic experiments were performed for 2 h under N₂ atmosphere using a 0.5 g L^-1 catalyst load and triethanolamine (0.2 M) acting as electron donor. Irradiation was provided by a LED system with a fixed excitation wavelength of 370 nm. H₂ production was monitored by online gas chromatography. The incorporation of the metal oxide resulted in a slight increase in the composites' light absorption and a substantial decrease in photoluminescence, suggesting a slower charge-carrier recombination rate. Among the catalysts, 0.5RuO₂/GCN showed the best photocatalytic performance, attaining a total H₂ production of 405 μmol after 2 h of reaction, while no H₂ was detected using neat GCN. These findings demonstrate that RuO₂ acts as a co-catalyst, enhancing charge carrier separation and providing active sites for proton reduction. This leads to improved photocatalytic H₂ production under mild operating conditions and supports the development of more efficient photocatalytic systems.