Influence of P,S,O-Doping on g-C₃N₄ for hydrogel formation and photocatalysis: An experimental and theoretical study

Photocatalysis is a facile and eco-friendly approach for the removal of dyes and organic compounds, water splitting, and CO₂ reduction and fixation. Herein we report the first use of P,S,O-co-doped graphitic carbon nitride (g-C₃N₄) to produce a photocatalyst hydrogel. The hydrogels are generated by photoinitiated crosslinking of N,N-dimethylacrylamide and N,N-methylenebis(acrylamide) with modified g-C₃N₄ materials and the photocatalytic activity is evaluated by monitoring the degradation of methyl blue (MB) solutions. S- or O-doping creates C‒S or C‒O bonds, respectively, by replacement N atoms, while P-doping produces P‒N bonds by substitution of C in the heptazine rings of g-C₃N₄. Based on a combination of theoretical calculations and experimental analyses, phosphorus, sulfur, and oxygen doping considerably facilitates charge separation across the heptazine rings and attracts photoexcited electrons, thus contributing to enhanced photocatalytic activity of doped g-C₃N₄. The P,S,O-co-doped g-C₃N₄ hydrogel exhibited high photocatalytic activity for MB removal under simulated solar irradiation and could be easily isolated and cleaned for reuse. Thus, this study reports the formation of a state-of-the-art photocatalyst hydrogel from P,S,O-co-doped g-C₃N₄ with enhanced photocatalytic activity and demonstrated reusability.