Bi-functional Cu-TiO2/CuO photocatalyst for large-scale synergistic treatment of waste sewage containing organics and heavy metal ions

Abstract

Numerous photocatalysts have been prepared for the photocatalysis of either organic pollutant degradation or Cr(VI) reduction. However, most of the inorganic and organic pollutants usually co-exist in industrial sewage. Simultaneous elimination of mixed inorganic and organic pollutants remains highly challenging. Herein, we report bi-functional Cu-TiO2/CuO photocatalysts by the in-situ doping and heterostructure engineering strategies for large-scale and highly enhanced synergistic photocatalytic elimination of organic pollutants and transitional metallic ions from waste sewage in one shot. Specifically, this bi-functional photocatalyst displays about 2.35 and 3.84 times higher photocatalytic Rhodamine B (RhB) degradation and Cr(VI) reduction rates in the solution with co-existing RhB and Cr(VI) than that in the single RhB or Cr(VI) pollutant solution, respectively. A highly boosted synergetic effect between photocatalytic dye molecule degradation and Cr(VI) reduction is revealed. The bi-functional photocatalyst also displays extraordinary activity and stability in large-scale photocatalytic elimination of mixed pollutants. Moreover, theoretical calculations demonstrate that Cu doping and heterostructure engineering give rise to the narrowed bandgap for enhanced light harvesting, the increased density of states for high charge carrier density, the delocalized electron for fast photoinduced charge carrier separation, and the profitable charge transfer between TiO2 and CuO, thus bringing about the efficient synergetic photocatalysis. The bi-functional photocatalyst concept reported in this study opens a new avenue to construct bi-functional photocatalysts for solar-to-fuel conversion and large-scale industrial waste water treatment and river purification.