Efficient visible-light driven photocatalytic Cr(VI) reduction on S and O co-doped g-C3N4 prepared from 2,5-thiophene dicarboxylic acid based macromolecular precursor

Elemental doping can improve the photocatalytic activity of bulk graphitic carbon nitride (g-C3N4) under visible-light. In this study, sulfur and oxygen co-doped g-C3N4 (x% S-g-C3N4) was fabricated through thermal polymerization of macromolecular precursor obtained from hydrothermal pretreatment. The prepared photocatalysts, including g-C3N4, hydrothermally treated g-C3N4 (g-C3N4-HT), and x% S-g-C3N4, were analyzed under various conditions. Their ability to reduce Cr(VI) through photocatalytic reduction was evaluated comprehensively, taking into account the influence of catalyst dose, presence of inorganic anions, initial concentration and initial pH of Cr(VI) solution. The results showed that x% S-g-C3N4 (3% S-g-C3N4) possesses superior photocatalytic reduction activity to g-C3N4 and g-C3N4-HT, largely due to the co-doping. This co-doping strategy enhances the light harvesting capacity by modifying the electronic band structure of g-C3N4, and accelerates the excitons transfer and separation by optimizing its photoelectric properties. Additionally, the three-dimensional structure formed during preparation process enhances the stability and reusability of g-C3N4.