Nanocomposites of C₃N₄ with Layers of MoS₂ and Nitrogenated RGO, Obtained by Covalent Cross-Linking: Synthesis,...

Generation of hydrogen by photochemical, electrochemical, and other means is a vital area of research today, and a variety of materials have been explored as catalysts for this purpose. C₃N₄, MoS₂, and nitrogenated RGO (NRGO) are some of the important catalytic materials investigated for the hydrogen evolution reaction (HER) reaction, but the observed catalytic activities are somewhat marginal. Prompted by preliminary reports that covalent cross-linking of 2D materials to generate heteroassemblies or nanocomposites may have beneficial effect on the catalytic activity, we have synthesized nanocomposites wherein C₃N₄ is covalently bonded to MoS₂ or NRGO nanosheets. The photochemical HER activity of the C₃N₄-MoS₂ nanocomposite is found to be remarkable with an activity of 12778 μmol h^-1 g^-1 and a turnover frequency of 2.35 h^-1. The physical mixture of C₃N₄ and MoS₂, on the other hand, does not exhibit notable catalytic activity. Encouraged by this result, we have studied electrochemical HER activity of these composites as well. C₃N₄-MoS₂ shows superior activity relative to a physical mixture of MoS₂ and C₃N₄. Density functional theory calculations have been carried out to understand the HER activity of the nanocomposites. Charge-transfer between the components and greater planarity of cross-linked layers are important causes of the superior catalytic activity of the nanocomposites. Covalent linking of such 2D materials appears to be a worthwhile strategy for catalysis and other applications.