Ca-CuFeO2/TiO2(B) heterojunctions
were constructed
to improve the photocatalytic reduction efficiency of Cr(VI). The
results suggest that Ca doping gives rise to the phase transition
of 3R to 2H, increased surface area, and improved charge transfer
ability of CuFeO2. Covering CuFeO2 with TiO2(B) effectively inhibits the partial oxidization of Cu1+ to Cu2+. The schematic energy band diagram and
carrier density distributions for Ca-CFO/TiO2 heterojunctions
were theoretically simulated using AMPS software. It suggests that
photogenerated electrons in the CuFeO2 conduction band
adjacent to the depletion region drift into TiO2(B) due
to the presence of a built-in electric field to directly participate
in the reducing process of Cr(VI) on the TiO2 surface.
Photogenerated holes in CuFeO2 can hardly drift or diffuse
into TiO2(B) due to the presence of an energy barrier in
the valence band and will diffuse to the uncovered CuFeO2 surface and be captured by formic acid to generate reactive CO2·– free radicals to effectively reduce
Cr(VI). The maximum photocatalytic efficiency using 5%Ca-CuFeO2/TiO2 (3:1) was 100% in 40 min. The study results
can provide a new avenue for the efficient treatment of Cr(VI)-containing
wastewater with Ca-CuFeO2/TiO2(B) p–n
heterojunctions owing to the advantages of high efficiency, environmental
friendliness, sustainability, and low energy consumption.
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