Operando Electrical Conductivity and Complex Permittivity Study on Vanadia Oxidation Catalysts

The electrical conductivity and its real and imaginary permittivity parameters were studied over two vanadium-containing catalysts for the selective oxidation of n-butane to maleic anhydride. Parameter variation under isothermal conditions allowed determination of multiple steady-state conditions for catalytic performance and charge carrier dynamics. One sample was the n-type semiconductor V2O5-x with low selectivity, and the other sample was the p-type semiconductor vanadyl pyrophosphate (VPP) with high selectivity for the target product. Well-resolved conductivity parameters supported by in situ UV-vis studies allowed correlations between performance and charge carrier dynamics. A concept for interpreting the trends is presented, and consequences for further analytical work as well as for material design are derived.