Fast photoelectro-reduction of CrVI over MoS2@TiO2 nanotubes on Ti wire.

A stable MoS2 nanosheets@TiO2 NTAs composite was prepared via a simple hydrothermal process. Few-layer MoS2 nanosheets distributed on the TiO2 nanotube top surface and the inner walls rather than filling in the tubes, allowing abundant tubular channels open to environment and benefiting for efficient mass transport. Photocatalytic (PE) and photoelectrocatalytic (PEC) performance of the composite were evaluated on CrVI reduction, with variable low molecule weight organic acids (LOAs) added as sacrificial electron donor to form a charge-transfer-complex (CTC) between LOAs and TiO2/MoS2, which is sensitive to the visible light illumination and could induce the photo-reduction of CrVI and photo-oxidation of LOAs. The overall trend of CrVI PEC rates are in the order as: L(+)-Tartaric acid>oxalic acid>citric acid>malic acid>amber acid, which is 103.9>62.5>31.2>21.6>2.5mg/Lmin-1cm-2, respectively. The improved catalytic performance and excellent stability of the composite can be attributed to the abundant active adsorption and reaction sites on MoS2 nanosheets and the formation of a heterojunction between TiO2 and MoS2. Moreover, the appropriate application of LOAs and voltage also have a great contribution to the utilization of sunlight and efficient separation of photogenerated carriers.