Design of S-scheme 3D nickel molybdate/AgBr nanocomposites: Tuning of the electronic band structure towards efficient interfacial photoinduced charge separation and remarkable photocatalytic activity

Abstract

We reported the facile synthesis of new S-scheme 3D NiMoO4/AgBr nanocomposites photocatalysts and their promising photoactivity for the methylene blue degradation. For efficient separation and transfer of charge carriers, heterojunction construction is desirable. The nickel molybdate heterostructured photocatalysts were fabricated by using facile template free hydrothermal and precipitation methods. The α-phase has doubly ionized vacancies and the β-phase has singly ionized vacancies, which makes the structures promising materials for photocatalytic applications. The fabricated photocatalysts were fully characterized. Photocurrent-time experiments, PL spectroscopy, and EIS were applied for charge carrier transfer, recombination and resistance investigations. Optical behavior of samples was analyzed by DRS technique and Tauc method and effect of different parameters on photoactivity was evaluated. The photocatalytic activity of NiMoO4/AgBr nanocomposite was larger than that of bare NiMoO4 and AgBr. Based on quenching method, it can be concluded that holes and hydroxyl radicals were the main active species and according to Langmuir-Hinshelwood kinetics model, the reaction obeyed the pseudo first order kinetics. High photocatalytic activity was related to the synergistic effect induced by formation of 3D NiMoO4/AgBr nanostructures. Active site on the surface of 3D NiMoO4/AgBr structure, high surface area, band structure and efficient charge separation and transfer through the NiMoO4/AgBr, are other effective factors on photodegradation. No morphology and structure changes observed after 4 consecutive cycle which concluded that the nanocomposites are chemically stable and can be used for practical cases.