Construction of Z-scheme CdS/Ag/TiO2 NTs photocatalysts for photocatalytic dye degradation and hydrogen evolution

The ternary CdS/Ag/TiO2 NTs photocatalysts with indirect Z-scheme heterojunctions were synthesized by the photoreduction deposition of Ag and successive ionic layer adsorption and reaction (SILAR) of CdS on TiO2 nanotube arrays (TiO2 NTs). The elemental composition, microstructure, photoresponse and photoelectrochemical property of the photocatalyst were systematically characterized. The results proved that compared with binary heterojunction, the light absorption range of the ternary CdS/Ag/TiO2 NTs photocatalyst was significantly extended, and the photoelectron transportation efficiency was improved. Under sunlight irradiation, the photocatalytic capacity was verified by investigating the photodegradation of MB and RhB dyes. The CdS/Ag/TiO2 NTs exhibited the optimal photocatalytic performance with the degradation efficiency of 82.24% for RhB and 100% for MB. The synthesized CdS/Ag/TiO2 NTs had high photocatalytic hydrogen evolution capacity and stability, and the hydrogen production reached 806.33 μmol·cm-2. Based on the results of electron spin resonance spectroscopy (ESR) and free radical trapping, the photocatalytic reaction mechanism was explained. The synthesis of ternary CdS/Ag/TiO2 NTs provides a practical reference and guidance for designing high-efficient photocatalysts with Z-scheme heterojunctions toward solar energy development for H2 generation, pollutant remediation and photoelectric conversion.