A novel n-p heterojunction Bi2S3/ZnCo2O4 photocatalyst for boosting visible-light-driven photocatalytic performance toward indigo carmine

Abstract

An innovative p-n heterojunction Bi₂S₃/ZnCo₂O₄ composite was first fabricated via a two-step co-precipitation and hydrothermal method. By controlling the weight amount of Na₂S and Bi(NO₃)₃ precursor, different heterogeneous xBi₂S₃/ZnCo₂O₄ were synthesized (x = 0, 2, 6, 12, and 20). The p-n heterojunction Bi₂S₃/ZnCo₂O₄ was characterized by structural, optical, and photochemical properties and the photocatalyst decoloration of indigo carmine. Mott-Schottky plots proved a heterojunction formed between n-Bi₂S₃ and p-ZnCo₂O₄. Furthermore, the investigation of the photocurrent response indicated that the Bi₂S₃/ZnCo₂O₄ composite displayed an enhanced response, which was respectively 4.6 and 7.3 times (4.76 μA cm^-2) greater than that of the pure Bi₂S₃ (1.02 μA cm^-2) and ZnCo₂O₄ (0.65 μA cm^-2). Especially the optimized p-n Bi₂S₃/ZnCo₂O₄ heterojunction with 12 wt% Bi₂S₃ showed the highest photocatalyst efficacy of 92.1% at 40 mg L^-1 solutions, a loading of 1.0 g L^-1, and a pH of 6 within 90 min of visible light illumination. These studies prove that p-n Bi₂S₃/ZnCo₂O₄ heterojunction photocatalysts can greatly boost their photocatalytic performance because the inner electric field enhances the process of separating photogenerated electron-hole pairs. Furthermore, this composite catalyst showed good stability and recyclability for environmental remediation.