Insights into enhanced visible-light photocatalytic activity of C-60 modified g-C3N4 hybrids: the role of nitrogen

Recent experiments have shown that the photocatalytic activity of g-C3N4 can be greatly enhanced by C-60 modification, however, a fundamental understanding of its mechanistic operation is still lacking. Using first-principles calculations, the interfacial effects of C-60/g-C3N4 nanocomposites on the electronic properties, charge transfer and optical response have been explored in detail. For different stacking patterns, the two constituents are always linked by van der Waals (vdW) forces without any exception, and form type-II heterojunctions in most cases. The valence band maximum and conduction band minimum of these heterostructures are dominated by the unsaturated nitrogen (N-2) atoms and C-60 molecule, respectively, which strongly interact with each other, resulting in strong charge transfer between the two involved constituents and an obvious bending of the g-C3N4 sheets. The unsaturated N-2 atoms included in the interfaces have a significant influence on promoting the photocatalytic performance, while the existence of saturated nitrogen (N-1 and N-3) atoms lying in the interfaces will weaken the interfacial interactions between C-60 molecules and the g-C3N4 monolayers. Moreover, the sensitive optical response and satisfactory type-II band alignment clearly show that the C-60/g-C3N4 heterostructure is an outstanding photocatalyst for hydrogen production. We proposed a deep insight (the role of nitrogen) into understanding the improved photocatalytic ability of the C-60/g-C3N4 nanocomposites, which may contribute to the rational design of both C-60/g-C3N4 and g-C3N4-based nanocomposite photocatalysts.