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

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.