Metal free S-scheme heterojunction S-doped g-C3N4/g-C3N4 for enhanced photocatalytic water splitting

Using different precursors (urea, thiourea, and urea-thiourea), the S(step)-scheme hetero system i. e. 2D/2D S-doped g-C3N4/g-C3N4 was synthesised by in-situ calcination. Samples that had been prepared were evaluated for water splitting to produce hydrogen in aqueous CH3OH scavenger under exposure of a 300W Xe light. The system consisting of urea and thiourea (1:1 CN-T + U) has exhibited the highest rate of hydrogen production i. e. 485.51 mu molg(-1)h(-1) with 1.75% apparent quantum efficiency (AQE) at 420 nm light irradiation, which is 1.37 and 1.29 times higher than the CN-U and CN-T systems. The S-type heterojunction formed between S-doped g-C3N4 and g-C3N4, is responsible for the higher rate of hydrogen evolution because the heterojunction is more efficient than the typical type-II heterojunction for spatial charge separation and redox ability of the system's oxidation and reduction sites. The photocatalytic electron transfer mechanism based on advanced analysis techniques (XRD, UV-Vis, SEM, EDX, PLE, ESR, XPS, SPV, etc.) was also suggested for the investigated system.