Photoelectrochemical properties of the perovskite BaSnO3 synthetized by chemical route. Application to electro-photocatalytic mineralization of ibuprofen

The perovskite BaSnO3, prepared by chemical route crystallizes in a cubic structure with an average crystallite size of 63 +/- 2 nm. The oxide is characterized by scanning electron microscopy, granulometry, optical properties and electrochemistry. The optical properties indicate a direct transition at 3.13 eV. The electrical conductivity follows an exponential law: sigma(o) exp (-E-a/kT) due to electronic hopping through mixed valences Sn4+/2+ in agreement with a semi conducting behavior. The intensity potential J(E) curve shows a small hysteresis and exhibits n-type behavior, indicating the presence of oxygen vacancies. The capacitance measurement at pH 5.5 gives a flat band potential of -0.37 VNHE. As application, the ibuprofen is eliminated by electrocatalysis on BaSnO3 with a conversion rate of 55% under a current of 150 mA. An increase up to 68% has been reached by electro-photocatalysis under UV illumination; the ibuprofen disappearance obeys to a first order kinetic with a rate constant of 3 x 10(-3) mn(-1) and a reaction mechanism is proposed.