α-Ag2WO4/g-C3N4: Investigation of the synthesis medium on composite properties and H2 evolution under simulated sunlight

Abstract

The current paper proposes a new approach to address the low separation rate of photogenerated charge carriers in g-C₃N₄ by decorating it with low concentrations of α-Ag₂WO₄. g-C₃N₄ and α-Ag₂WO₄ were prepared separately via urea pyrolysis and co-precipitation, respectively. The composites were then physically prepared using a sonication-grinding method. The effect of the preparation medium was considered a crucial aspect of this study. Two different media were examined: pure water and a water/ethanol mixture (50 % v/v). It was found that pure water was more favorable for achieving high photocatalytic performance compared to the ethanol/water mixture. The photocatalytic hydrogen production through ethanol photoreforming under simulated solar light was investigated. The results showed that α-Ag₂WO₄/g-C₃N₄ (w), prepared in pure water, exhibited significantly higher efficiency for H₂ production compared to both pure g-C₃N₄ and the series prepared in the ethanol/water solution. This improvement was attributed to the intimate contact between the two phases in the heterojunction when water was used as the preparation medium. The optimal photocatalyst, 2 % α-Ag₂WO₄/g-C₃N₄ (w), achieved an H₂ evolution rate of 110.28 μmol g⁻¹ h⁻¹, whereas pure g-C₃N₄ reached only 25.32 μmol g⁻¹ h⁻¹. The formation of a heterojunction between α-Ag₂WO₄ and g-C₃N₄ promotes the separation of photogenerated charge carriers and prolongs their lifespan, which is the primary reason for the enhanced H₂ evolution activity.