Fabrication of visible-light-active ZnO/ZnFe-LDH heterojunction on Ni foam for pollutants removal with enhanced photoelectrocatalytic performance

A visible-light-active Ni foam@ZnO@ZnFe-LDH composite photocatalyst was fabricated with well-defined porous 2D/2D interconnected nanosheets of ZnO and binary ZnFe layered double hydroxide (ZnFe-LDH) growing vertically on the Ni foam substrate. In view of the excellent conductivity of Ni foam, it can be used as an electrode substrate to deposit ZnO nanosheets on the surface by electrodeposition. Then the ultrathin layered 2D ZnFe-LDH was uniformly coated on ZnO nanosheets by hydrothermal method. A highly effective three-electrode photoelectrocatalytic (PEC) system was constructed with Ni foam@ZnO@ZnFe-LDH as photoanode. The 2D/2D core-shell heterojunction formed between ZnO core and ZnFe-LDH shell not only resulted in a narrowing bandgap and increased the visible light absorption of the ZnO, but also promoted the migration of the photo generated electrons and then the degradation efficiency with a low applied potential was greatly improved. The dyes (Acid Red 1 as model) and hexavalent chromium ions (Cr(VI)) in water can be simultaneously removed by oxidation reaction on the anode and reduction reaction on the cathode, respectively. In addition, the Ni foam@ZnO@ZnFe-LDH composite photocatalyst also showed outstanding stability during the application process. Thus, the photoelectrocatalytic synergitic effect based on Ni foam@ZnO@ZnFe-LDH gives a simple and effective strategy to fast remove Cr(VI) and organic pollutants in PEC process at low voltage.