Visible-light photocatalytic reduction of Cr(Ⅵ) using nano-sized delafossite (CuFeO2) synthesized by hydrothermal method

Developing p-type semiconductors by using simple and reliable synthesis procedure is a promising way to expand the field of photocatalytic application in fuel production and photo-reduction of inorganic contaminants. Herein, a potential p-type semiconductor, nano-sized CuFeO2 with large specific surface area and excellent photocatalytic activity was successfully synthesized by hydrothermal method. Various physicochemical and photoelectrochemical properties of this material were investigated. The as-prepared nano-sized CuFeO2 was verified to have a bandgap energy of ca. 1.15 eV and a more negative conduction band edge than the reduction potential of hexavalent chromium (Cr(Ⅵ)). It is thermodynamically feasible for using as-prepared nano-sized CuFeO2 as a photocatalyst to reduce Cr(Ⅵ) under visible-light irradiation. To find the optimal operation condition of photocatalytic reduction procedure, the essential influencing factors in terms of initial concentration of formic acid (hole scavenger), pH, and the dosage of nano-sized CuFeO2 were studied. Compared with micron-sized CuFeO2, as-prepared nano-sized CuFeO2 exhibits better photocatalytic performance for Cr(Ⅵ) reduction. The reduction efficiency on nano-sized CuFeO2 reaches 96% within 60 min. Moreover, the proposed mechanism of photocatalytic reduction process was also discussed in this work.