Enhanced photocatalytic Cr(VI) reduction and H2 production of CdSe quantum dots supported on Co-encapsulated N-doped carbon

Background: Solar-driven water splitting is regarded as one promising green way to produce H-2. Photo-reduction of hexavalent chromium (Cr(VI)) to hypotoxic Cr(III) can control the Cr(VI)-induced pollution. A key in these processes is to develop a photocatalyst with high specific surface area, good light absorption and efficient charge carrier separation. Methods: A Co-encapsulated N-doped carbon (Co@NC) was prepared by pyrolysis ZIF-8@ZIF-67 precursor to modify CdSe quantum dots (QDs). The obtained catalyst was used to reduce Cr(VI) and split water under visible light irradiation. Significant findings: Modification CdSe with Co@NC made obtained Co@NC/CdSe possessing enhanced visible-light absorption and photoexcited charge separation. The optimal 2%Co@NC/CdSe exhibited the excellent Cr (VI) reduction performance with a rate constant of 0.28 min(-1) in the absence of sacrificial agent, as well as high H-2 evolution rate of 6.48 mmol g(-1) h(-1) in 10% lactic acid solution. The H2O2 and electrons were the active species to reduce Cr(VI). This work gives a beneficial insight for improving the photocatalytic activity of QDs.