Cu 2 O/SrTi 1- x Cr x O 3 Heterojunction Photocatalyst for the Efficient Degradation of Isopropanol under Visible Light Irradiation.

A heterojunction of Cu 2 O and Cr-doped SrTiO 3 (SrTi 1- x Cr x O 3 ) was designed for selective photocatalytic isopropanol (IPA) oxidation under visible light irradiation. The photocatalytic oxidation of IPA was measured in a fixed-bed reactor. Cr dopants can increase the light absorption and improve the activity of the catalyst. The formation of the Cu 2 O/SrTi 1- x Cr x O 3 heterojunction can further broaden the absorption range of lights and dramatically increase the photocatalytic activity for selective oxidation of IPA. The 3% Cu 2 O/SrTi 0.99 Cr 0.01 O 3 catalyst can fully convert ∼1000 ppm IPA under illumination in 2 h. The selectivity of acetone is ∼100%. The yield is 83 and 4 times higher than that using SrTiO 3 and SrTi 0.99 Cr 0.01 O 3 as catalysts, respectively. By measuring the ultraviolet-visible absorption spectra and Mott-Schottky plots, we obtained the band structure of the heterojunction, which shows that the conduction and valence bands of Cu 2 O are higher than those of SrTi 1- x Cr x O 3 , therefore facilitating the separation and transfer of photogenerated electrons and holes. In addition, electron paramagnetic resonance spectroscopy and radical trapping tests reveal that the generation of hydroxyl and superoxide leads to photocatalytic oxidation of IPA by the heterojunction photocatalyst.