Abstract: The development of highly efficient catalyst is the key for photocatalytic technology to deal with water pollution and energy problems. In this work, the S-scheme polyaniline/Cd_0.5Zn_0.5S (PANI/CZS) nanocomposites were elaborately prepared for the first time by in-situ oxidation polymerization. Compared to pure PANI and Cd_0.5Zn_0.5S, this PANI/CZS hybrid displayed outstanding photocatalytic performance in removing tetracycline hydrochloride (TCH) and hydrogen evolution under light irradiation. Among them, 15 PANI/CZS sample could achieve 84.9% TCH degradation efficiency within 25 min, and the degradation rate (0.06931 min^-1) was 5.13 times than that of Cd_0.5Zn_0.5S (0.0135 min^-1). The optimal photocatalytic H₂ evolution rate of 30 PANI/CZS sample was 15.57 mmol g^-1 h^-1, which was twice that of Cd_0.5Zn_0.5S (7.34 mmol g^-1 h^-1). These results were mainly attributed to the efficient electronic transport channels provided by S-scheme heterojunction structure. The density functional theory (DFT) calculation proved that the difference of work function resulted in band bending and forming built-in electric field on the contact interface of PANI/CZS, which facilitated the migration and separation of interfacial photogenerated charge carriers for the strengthened photocatalytic performance. Further, the degradation intermediate products and pathways of TCH were also put forwarded in depth based on MS experiment. At last, the S-scheme electron transport model and the photocatalytic reaction mechanism in PANI/CZS heterojunction structure were studied. This work provided an innovative vision in developing high-performance S-scheme heterojunction multifunctional photocatalysts.

Key words: S-scheme heterostructure, Cd_0.5Zn_0.5S, PANI, H₂ evolution, TCH photodegradation