Fast photoelectro-reduction of Cr^VI 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 Cr^VI 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 Cr^VI and photo-oxidation of LOAs. The overall trend of Cr^VI 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.