A novel n-p heterojunction Bi 2 S 3 /ZnCo 2 O 4 photocatalyst for boosting visible-light-driven photocatalytic performance toward indigo carmine.

An innovative p-n heterojunction Bi 2 S 3 /ZnCo 2 O 4 composite was first fabricated via a two-step co-precipitation and hydrothermal method. By controlling the weight amount of Na 2 S and Bi(NO 3 ) 3 precursor, different heterogeneous x Bi 2 S 3 /ZnCo 2 O 4 were synthesized ( x = 0, 2, 6, 12, and 20). The p-n heterojunction Bi 2 S 3 /ZnCo 2 O 4 was characterized by structural, optical, and photochemical properties and the photocatalyst decoloration of indigo carmine. Mott-Schottky plots proved a heterojunction formed between n-Bi 2 S 3 and p-ZnCo 2 O 4 . Furthermore, the investigation of the photocurrent response indicated that the Bi 2 S 3 /ZnCo 2 O 4 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 Bi 2 S 3 (1.02 μA cm -2 ) and ZnCo 2 O 4 (0.65 μA cm -2 ). Especially the optimized p-n Bi 2 S 3 /ZnCo 2 O 4 heterojunction with 12 wt% Bi 2 S 3 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 Bi 2 S 3 /ZnCo 2 O 4 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.