TiO2-coated copper zinc tin sulfide photocatalyst for efficient photocatalytic decolourization of dye-containing wastewater

A hierarchical composite of TiO2 coated on Cu2ZnSnS4 (CZTS/TiO2) with various molar ratios was synthesized by hydrothermal process combined with subsequent grinding and low-temperature calcination. The optimal molar ratio of CZTS to TiO2 in CZTS/TiO2 composites is 1:1. Due to the staggered band structure of CZTS and TiO2, the designed CZTS/TiO2 superstructure extends the light absorption of TiO2 into visible region and even separates photoinduced carriers well so that it presented higher photocatalytic activity than pristine CZTS and anatase TiO2. The photodegradation efficiency (PE) of aqueous RhB solution (10 mg/L) reached 95.04% with 120 min. Furthermore, the photodegradation reaction obeyed the first-order kinetics, which the apparent rate constant (kapp) was 4.87 and 2.70 times higher than that of pure CZTS and TiO2, respectively. More importantly, the synthesized CZTS/TiO2 composites exhibited excellent durability and recyclability in the photocatalytic process. Even after using for four times, the photocatalytic activity was hardly any decay. The PE decreased significantly with increasing pH of dye solutions. At pH of 2–6, at least 85% of the dye solution was degraded. Studying critical role of h+ and •O2− radicals involved in RhB decomposition. The results indicates that CZTS/TiO2 photocatalyst could act as a perspective candidate in wastewater purification applications.