Fabrication and characterization of a novel Fe(Ⅲ) modified C-doped Cr2O3 photocatalyst for cyclohexane oxidation to cyclohexanone with ultrahigh selectivity

Abstract

The grafting of Fe(Ⅲ) cocatalysts onto the surface of C-doped Cr2O3 derived from MIL-101(Cr) has been successfully achieved via a simple precipitation. The obtained Fe(Ⅲ) modified C-doped Cr2O3 photocatalyst has been investigated by cyclohexane oxidation to cyclohexanone and some physicochemical characterizations like XRD, BET, ICP-MS, SEM TEM XPS FT-IR, SPV, PL, ESR and UV–vis-DRS. The results reveal that the Fe species are exited in a +3 state and uniformly disperse on the surface of the C-doped Cr2O3. The Fe@C/Cr2O3 samples possess a broad visible light absorption region and exhibit super photocatalytic activity and selectivity for cyclohexane oxidation to cyclohexanone. Fe(Ⅲ)could be considered as a reduction site for largely improving the formation of superoxide radical anion from oxygen molecule in the photocatalytic reaction, which induces a high photocatalytic activity for cyclohexane oxidation. Compared with C/Cr2O3, the photocatalytic activity of Fe@C/Cr2O3 could be increased by up to six times at room temperature. Moreover, the ultrahigh selectivity (99.77%) for cyclohexanone is obtained. The high photocatalytic activity and cyclohexanone selectivity is attributed to the improved generation of cyclohexyl radicals and superoxide radical anions due to the Fe(Ⅲ)modified surface of C-doped Cr2O3photocatalyst under the controlled photocatalytic reaction condition.