Influence of Zn/Co ratio and calcination temperature on the visible light-driven photoelectrocatalytic properties of ZnCoIn-LDOs for the reduction of Cr(VI)

A series of ZnCoIn-LDOs were successfully prepared by the calcination of ZnCoIn-LDH precursors under different Zn/Co ratios and temperatures. The composition, structure, and visible light response of the composites were systematically investigated. A photoelectric catalytic performance test showed that the optimal Zn/Co/In ratio and calcination temperature were 2:1:1 and 550 °C, respectively. After 100 min of photoelectrocatalytic reaction under simulated sunlight exposure, Cr(VI) conversion rate reached 100%. According to the characterization of ZnCoIn-LDOs, it was revealed that the composites had typical p-n heterojunction structure which was beneficial for the transfer and transmission of photogenerated electrons and suppressing the complexation of electron–hole pairs effectively. In addition, appropriate Zn/Co/In ratio and calcination temperature significantly reduced the forbidden band width of the composites and thus improved the electron leap and the photocatalytic performance on the reduction of Cr(VI). Finally, a possible mechanism for the reduction of Cr(VI) was proposed by free radical analysis. It can be concluded that ·H plays an important role in the catalytic reduction of Cr(VI) in solution. In summary, the present work provides a promising method for the preparation of efficient photocatalytic electrode using ZnCoIn-LDOs, which can be used in photoelectrocatalytic reduction field.