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

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.