Fabrication of a dual S-scheme S-doped g-C3N4/In2S3/TiO2 muti-heterojunction photocatalyst for significantly enhanced photocatalytic degradation performance toward organic pollutants

Dual S-scheme heterojunctions exhibit unique advantages in multi-heterojunction photocatalysts. Rational design of dual S-scheme heterojunction systems is of great significance for the development of photocatalytic technology. In this work, an S-doped g-C3N4/In2S3 (S-C3N4/In2S3) dual-phase heterojunction was constructed via a simple ball-milling technique. The S-C3N4/In2S3/TiO2 photocatalyst achieves efficient degradation of rhodamine B and tetracycline (TC), showing significantly enhanced photocatalytic activity. Meanwhile, the photocatalytic performance tests under different pH and anion environments demonstrate that an acidic environment favors the effective removal of TC by S-C3N4/In2S3/TiO2, while HCO3⁻ and CO3²⁻ exert obvious inhibitory effects on the photocatalytic process. Through in-depth mechanistic investigations and analyses, the S-C3N4/In2S3/TiO2 multi-heterojunction system follows a dual S-scheme photogenerated charge transfer pathway, enabling efficient separation and migration of photogenerated carriers and generating abundant reactive oxygen species to participate in the photocatalytic process, thereby effectively improving the photocatalytic performance of S-C3N4/In2S3/TiO2.