Comparative study of the photocatalytic activity of g-C3N4/MN4 (M = Mn, Fe, Co) for water splitting reaction: A theoretical study

In this study, nanocomposites of g-C₃N₄/MN₄ (where M is Mn, Fe and Co) have been designed using advanced density functional theory (DFT) calculations. A comprehensive analysis was conducted on the geometry, electronic, optical properties, work function, charge transfer interaction and adhesion energy of the g-C₃N₄/MN₄ heterostructures and concluded that g-C₃N₄/FeN₄ and g-C₃N₄/CoN₄ heterojunctions exhibit higher photocatalytic performance than individual units. The better photocatalytic activity can be attributed mainly by two facts; (i) the visible light absorption of both g-C₃N₄/FeN₄ and g-C₃N₄/CoN₄ interfaces are higher compared to its isolated analogs and (ii) a significant enhancement of band gap energy in g-C₃N₄/FeN₄ and g-C₃N₄/CoN₄ heterostructures limited the electron–hole recombination significantly. The potential of the g-C₃N₄/MN₄ heterojunctions as a photocatalyst for the water splitting reaction was assessed by examining its band alignment for water splitting reaction. Importantly, while the electronic and magnetic properties of MN₄ systems were studied, this is the first example of inclusion of MN₄ on graphene-based material (g-C₃N₄) for studying the photocatalytic activity. The state of the art DFT calculations emphasis that g-C₃N₄/FeN₄ and g-C₃N₄/CoN₄ heterojunctions are half metallic photocatalysts, which is limited till date.