Preparation and photocatalytic properties of g-C3N4/WO3–SiO2 composite photocatalyst for methylene blue and methyl orange degradation

WO3–SiO2 gel was prepared by sol-gel method using ethyl orthosilicate and sodium tungstate dihydrate as raw materials, and a series of g-C3N4/WO3–SiO2 composite photocatalysts with different g-C3N4 loading loads were prepared on WO3–SiO2 gel. The photocatalytic degradation performance of methylene blue (MB) and methyl orange (MO) was investigated under 464 nm light source. According to the findings, the degrading effect of the g-C3N4/WO3–SiO2 composite catalyst is optimum when the load of g-C3N4 is 1.3 wt%, and the degradation rates of MB and MO are 95.62 % and 98.09 %, respectively. The characterization results show that the excellent photocatalytic performance is due to the formation of g-C3N4/WO3 heterojunction by the introduction of g-C3N4, which effectively promotes the migration and separation of photogenerated carriers, increases the number of active electrons and holes, and thus enhances its photocatalytic activity. In addition, according to the analysis of the energy band structure of the catalyst, the possible mechanism of g-C3N4/WO3–SiO2 degradation of MB (MO) is proposed as S-type heterojunction mechanism.