Construction of Bi-assisted modified CdS/TiO2 nanotube arrays with ternary S-scheme heterojunction for photocatalytic wastewater treatment and hydrogen production

A composite Bi/CdS/TiO2 nanotube arrays (TiO2 NTs) photocatalyst with remarkable photocatalytic performance was prepared by the successive ionic layer adsorption and reaction (SILAR) method. The crystallinity of the samples was determined by XRD and TEM, and the SEM results showed the successful formation of Bi and CdS. The excellent photocatalytic performance of CdS/Bi/TiO2 NTs was confirmed by the degradation of rhodamine B (RhB), methylene blue (MB) and the reduction of Cr(VI), specifically, the removal efficiency reached 100 % toward MB degradation after 2 h irradiation, 85.41% and 97.04% for RhB and Cr(VI) after 3 h irradiation. In addition, CdS/Bi/TiO2 NTs exhibited stable electrochemical properties. The S-scheme heterostructure photocatalytic mechanism was proposed based on the energy band structure calculation and radical formation analysis from electron spin resonance (ESR). The hydrogen production rate of CdS/Bi/TiO2 NTs reached 673.81 μmol·h−1·cm−2, and the high stability of CdS/Bi/TiO2 NTs was exhibited in the cycling test of hydrogen production and dye degradation, confirming the stability improvement role of Bi nanoparticles.