A research on the visible light photocatalytic activity and kinetics of CdS/CdSe co-modified TiO2 nanotube arrays

CdS and CdSe nanoparticles (NPs) were deposited on highly ordered TiO2 nanotube arrays (NTAs) by chemical bath deposition (CBD) and electrodeposition methods. FESEM, XRD, HRTEM, XPS, UV–Vis and EDX methods were employed to characterize the microstructure and composition of samples. CdSe and CdS nanoparticles were found to be uniformly deposited on the wall of TiO2 nanotubes after 10 controlled deposition cycles of CdS and a period of 600s deposition of CdSe. The photocatalytic performances of TiO2, CdS/TiO2, CdSe/TiO2 and CdSe/CdS/TiO2 NTAs were systematically investigated. Both single modification and co-modification extended the light absorption of TiO2 NTAs to the visible light range. The degradation rate of CdSe/CdS/TiO2 NTAs to Methyl Orange solution reached 96.0% after being irradiated in the visible light (250W metal halide lamp) for 2h, and remained at 84.3% after being reused for 15 times. Comparatively, the degradation rates of CdSe/TiO2 and CdS/TiO2 NTAs to Methyl Orange solution for the first use were just 92.8% and 89.8% respectively. Kinetic research shows that the apparent reaction rate constants for CdS/TiO2, CdSe/TiO2 and CdSe/CdS/TiO2 NTAs are 0.01889, 0.02176 and 0.02701min−1 respectively. •CdS and CdSe nanoparticles were deposited on TiO2 NTAs by two steps.•Uniform distribution of nanoparticles was achieved by controlling deposition.•CdSe/CdS/TiO2 NTAs show 96.0% degradation rate after visible light irradiation.•The reaction rate constant of CdSe/CdS/TiO2 NTAs was 0.02701min−1.•Degradation rate of CdSe/CdS/TiO2 NTAs keeps at 84.3% after reused for 15 times.