Innovative multi-Z-scheme Bi2MoO6/BiOBr0.75/BiOI0.25/g-C3N4 quaternary composite with superior visible-light photocatalytic performance for degrading rhodamine B and furfural

Abstract

The innovation of this work lies in the integration of four semiconductors (Bi₂MoO₆, BiOBr, BiOI and g-C₃N₄) in a single quaternary composite, designed to improve photocatalytic efficiency by reducing electron-hole recombination and increasing the specific surface area compared to that of each of the four components. A novel quaternary hybrid composite with heterojunction, named Bi₂MoO₆/BiOBr_0.75/BiOI_0.25/25 %-g-C₃N₄, was developed by optimizing the g-C₃N₄ content using a simple and efficient solvothermal approach without the need for thermal treatment. The photocatalyst was characterized using various techniques including XRD, ATR, SEM-EDS, EDS-mapping, BET, XPS, UV–visible DRS, and PL. Its photocatalytic performances were assessed for the degradation of Rhodamine B (RhB) and furfural under visible light irradiation. The Bi₂MoO₆/BiOBr_0.75/BiOI_0.25/25 %-g-C₃N₄ composite showed significantly higher photocatalytic efficiency than other synthesized materials, achieving remarkable degradation rates of 99.47 % for RhB (15 mg/L) and 82.78 % for furfural (100 mg/L) within 120 min. Through the identification of the radical species involved in the process, a photodegradation mechanism was proposed. Indeed, for RhB degradation, the main reactive species were holes (h⁺), with electrons ($e^{-}$) playing a secondary role. In contrast, for furfural degradation, hydroxyl radicals (HO^·) were the main contributors, while holes (h⁺) and superoxide radicals ($O_2^{•-}$), contributed equally but to a lesser extent.