Photoelectrochemical properties of Ba2TiO4 prepared by nitrate route. Application to electro-photocatalysis of phenobarbital mineralization by solar light

Ba2TiO4 elaborated from nitrates decomposition crystallizes in a monoclinic perovskite structure with a crystallite size of 66 +/- 2 nm and is applied for the environmental protection. The oxide is characterized by scanning electron microscopy, diffuse reflectance and photo-electrochemistry; an indirect transition at 3.34 eV is determined. The electrical conductivity follows an exponential law: sigma(o) exp (-0.40 eV/kT) and the conduction occurs by small polarons hopping through mixed valences Ti4+/3+ with a semi conductor behavior. The intensity potential J(E) characteristic in Na2SO4 (10(-2) M, pH similar to 6) exhibits a small hysteresis similar to a chemical diode. The capacitance measurement recorded at pH similar to 6 indicates and n-type behavior, due to oxygen vacancies and gives a flat band potential of 0.74 V-SCE. As application, the phenobarbital is successfully oxidized by electro-catalysis on Ba2TiO4 with a conversion rate of 55% under an electric current of 120 mA. An enhancement up to 66% has been obtained by electro-photocatalysis under solar illumination. The phenobarbital elimination follows a first order kinetic with a rate constant of 3.22 x 10(-3) mn(-1) and a reaction mechanism is suggested.