Improved photocatalytic reduction of Cr(VI) by molybdenum disulfide modified with conjugated polyvinyl alcohol

In this work, a novel efficient photocatalyst comprising molybdenum disulfide (MoS2) nanosheets and conjugated polyvinyl alcohol (CPVA) has been successfully synthesized. To effectively coat the conjugated polyvinyl alcohol on the surface of molybdenum disulfide, molybdenum disulfide nanosheets were first modified to hydroxylated molybdenum disulfide (MoS2-OH) using 2-mercaptoethanol. The morphologies, chemical compositions, crystal phases and optical properties of the obtained CPVA/MoS2-OH were characterized. The results showed the CPVA was successfully coating onto MoS2 nanosheets, and improved the light absorption, electron transport ability and charge transfer ability of MoS2. The obtained CPVA/MoS2-OH presented a significant enhancement of photoactivity towards chromium (VI) reduction. The CPVA/MoS2-OH-1wt% with the filling ratio of CPVA: MoS2-OH at 1:100 exhibited the best photocatalytic activity, in which the chromium (VI) reduction efficiency was 96% (Simulated sunlight, 105 min). The corresponding rate constant was approximately 2.27 times higher than that of neat MoS2. The improvement in catalytic performance might be due to the enhanced light absorption and electron transport capacity resulted from the photocurrent response tests and free radical capture experiments. In addition, the effect of the dosage of photocatalyst, Cr(VI) solution concentrations and pH of Cr(VI) aqueous solution on the catalyst performance for CPVA/MoS2-OH-1wt% were investigated.