Synthesis of Bi 2 S 3 /BiVO 4 Heterojunction with a One-Step Hydrothermal Method Based on pH Control and the Evaluation of Visible-Light Photocatalytic Performance

摘要

The band gaps of bismuth vanadate (BiVO 4 ) and bismuth sulfide (Bi 2 S 3 ) are about 2.40 eV and 1.30 eV, respectively. Although both BiVO 4 and Bi 2 S 3 are capable of strong visible light absorption, electron–hole recombination occurs easily. To solve this problem, we designed a one-step hydrothermal method for synthesizing a Bismuth sulfide (Bi 2 S 3 )/Bismuth vanadate (BiVO 4 ) heterojunction using polyvinylpyrrolidone K-30 (PVP) as a structure-directing agent, and 2-Amino-3-mercaptopropanoic acid ( l -cysteine) as a sulfur source. The pH of the reaction solution was regulated to yield different products: when the pH was 7.5, only monoclinic BiVO 4 was produced (sample 7.5); when the pH was 8.0 or 8.5, both Bi 2 S 3 and BiVO 4 were produced (samples 8.0 and 8.5); and when the pH was 9.0, only Bi 2 S 3 was produced (sample 9.0). In sample 8.0, Bi 2 S 3 and BiVO 4 were closely integrated with each other, with Bi 2 S 3 particles formed on the surface of concentric BiVO 4 layers, but the two compounds grew separately in a pH solution of 8.5. Visible-light photocatalytic degradation experiments demonstrated that the degradation efficiency of the Bi 2 S 3 /BiVO 4 heterojunction was highest when prepared under a pH of 8.0. The initial rhodamine B in the solution (5 mg/L) was completely degraded within three hours. Recycling experiments verified the high stability of Bi 2 S 3 /BiVO 4 . The synthesis method proposed in this paper is expected to enable large-scale and practical use of Bi 2 S 3 /BiVO 4 .