Insights into enhanced visible-light photocatalytic activity of C60 modified g-C3N4 hybrids: the role of nitrogen

Abstract

Recent experiments have shown that the photocatalytic activity of g-C₃N₄ can be greatly enhanced by C₆₀ modification, however, a fundamental understanding of its mechanistic operation is still lacking. Using first-principles calculations, the interfacial effects of C₆₀/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 (N₂) atoms and C₆₀ 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 N₂ atoms included in the interfaces have a significant influence on promoting the photocatalytic performance, while the existence of saturated nitrogen (N₁ and N₃) atoms lying in the interfaces will weaken the interfacial interactions between C₆₀ molecules and the g-C₃N₄ monolayers. Moreover, the sensitive optical response and satisfactory type-II band alignment clearly show that the C₆₀/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 C₆₀/g-C₃N₄ nanocomposites, which may contribute to the rational design of both C₆₀/g-C₃N₄ and g-C₃N₄-based nanocomposite photocatalysts.