Combination of Broad Light-Absorption Cu₉S₅ with S,C,N-TiO₂: Assessment of Photocatalytic Performance in Nitrogen Fixation Reaction

In the field of solar energy storage, photocatalytic ammonia production is a next-generation technology. The rapid recombination of charges and insignificant utilization of the sunlight spectrum are bottlenecks of effective photocatalytic N₂ fixation. The introduction of impurities in the crystal lattice and the development of heterojunctions could effectively segregate carriers and improve the solar-light-harvesting capability, which can boost NH₃ generation. Therefore, in this work, three-element doping by S, C, and N was carried out to rectify the photocatalytic feature of TiO₂, and then it was combined with a broad-light-absorption Cu₉S₅ semiconductor. The synthesized S,C,N-doped TiO₂/Cu₉S₅ nanocomposites with a QD size of almost 7.17 nm exhibited outstanding ability in photocatalytic N₂ reduction, and the generation of NH₃ reached 23 567 μmol L^-1 g^-1 without sacrificial agents, which was 5.67 and 2.11 folds larger than TiO₂ and Cu₉S₅, respectively. The promoted performance of the nanocomposite was ascribed to doping three elements and the construction of a Z-scheme system, which attains efficacious separation of carriers and supplies a dedicated path for carrier migration. This research not only supports a novel, sustainable, and facile strategy for the synthesis of S,C,N-TiO₂/Cu₉S₅ nanocomposites with inorganic materials and biocompatible characteristics but also provides new insights into the design and construction of TiO₂-based materials through nonmetal and low-cost three-elemental doping for photocatalytic nitrogen fixation.