CS-biochar/ZnO/TiO₂ for efficient photocatalytic removal of Rhodamine B: performance and mechanism insights

Based on the excellent adsorption, photosensitization and electron transfer ability of biochar, the combination of photocatalyst and biochar is an effective method to improve the overall photocatalytic activity. Hence, a novel efficient CS-biochar/ZnO/TiO₂ photocatalyst with the different content of N-doped porous CS-biochar were constructed and characterized by a variety of testing methods, such as FT-IR, XRD, UV–vis DRS, SEM–EDS, PL, EIS, TPR, LSV. Photocatalytic experiments indicated that all the CS-biochar/ZnO/TiO₂ composites with different CS-biochar content exhibit excellent photocatalytic activity for Rh B degradation. Among them, 63%-CS/ZnO/TiO₂ composite has the best catalytic activity, which 94.5% of Rh B was degraded within 25 min, and the kinetic constant was 0.0993 min⁻¹, which is about 1.96 and 1.72 times that ZnO (0.0507 min⁻¹) and TiO₂ (0.0576 min⁻¹), respectively. Moreover, photoelectrochemical experiment results confirmed that CS-biochar/ZnO/TiO₂ greatly enhanced the charge separation process compare with ZnO and TiO₂. Meanwhile, CS-biochar/ZnO/TiO₂ has excellent stability, and a possible photocatalytic mechanism was put forward.