Enhanced Photocatalytic Activities of Ag₂WO₄ Modified Ag₆Si₂O₇ through a Comprehensive p-n Heterojunction S-Scheme Process

Abstract

The S-scheme photocatalyst system has become increasingly popular in recent years for its ability to efficiently degrade various pollutants, including organic dyes, pesticides, and other harmful substances. This system uses two semiconductor photocatalysts with different bandgap energies, working together in a redox reaction to produce a highly reactive species capable of pollutant breakdown. Here, an S-scheme Ag2WO4/Ag6Si2O7 p-n heterojunction nanocomposite was successfully developed by a coprecipitation method. By decomposing Rhodamine B (RhB) under visible-light irradiation, the photocatalytic activities of Ag6Si2O7/Ag2WO4 showed enhanced photocatalytic degradation performance of organic dyes, especially at a 4% molar ratio of the Ag2WO4-modified Ag6Si2O7 sample, whose degradation rate was 23.7 and 4.65 times those of Ag2WO4 and Ag6Si2O7, respectively. The physical and chemical properties of the samples were determined by identifying the physical structure, chemical element composition, and optical responsiveness. The optimum composite amongst the prepared materials was AgSW-4, achieving the maximum RhB degradation efficiency of 97.5%, which was higher by 60% and 20% than its counterparts Ag6Si2O7 and Ag2WO4, respectively. These results showed that in the nanocomposite structure, Ag6Si2O7 was a p-type semiconductor and Ag2WO4 was an n-type semiconductor. Based on the analysis data, a comprehensive p-n heterojunction S-scheme process was proposed to demonstrate the enhanced photocatalytic performance of the Ag6Si2O7/Ag2WO4 nanocomposite.

Keywords

• silver tungstate
• silver silicate
• S-scheme
• p-n heterojunction