Verification of impurity-related photocatalytic activity of insulating oxide supports

Photocatalysts composed of vanadium oxide species supported on commercial MgO and ZrO2 are investigated in selective methanol oxidation. Both support oxides are insulators, so the vanadium oxide species are expected as sole active component in photocatalysis. However, the pure supports showed considerable activity: Bare MgO was more active than MgO-supported vanadia catalysts, and ZrO2 showed intermediate activity. By various characterization methods, the presence of TiO2 (anatase) in the MgO support, and the presence of Zn, possibly as ZnO, in ZrO2 is demonstrated. The present study highlights that photocatalysts containing commercial supports must be carefully checked for impurity-related photocatalytic performance. [Display omitted] •Commercial MgO and ZrO2 display apparent activity in photocatalytic oxidation.•Anatase TiO2 impurity is found in MgO.•Zn impurities, presumably ZnO, detected in ZrO2.•Impurities mainly responsible for photocatalytic activity, even in presence of VOx.