Photoelectrochemical properties of CaWO4 synthetized by chemical route. Application to the phenobarbital electro-photocatalysis

Abstract

Abstract The semiconducting properties of the Scheelite CaWO4, synthesized by nitrate route, were investigated by the photocurrent technique and capacitance measurements in acidic solution (pH ∼ 5). CaWO4 crystallizes in the tetragonal symmetry with a large optical gap (4.88 eV) and a low electrical conductivity (σ300K = 2.63 × 10−5 Ω−1 cm−1). The photo-electrochemical characterization shows n type semi conductivity with a wide depletion length (∼110 nm). The Nyquist representation, measured in the range (10−3–105 Hz), indicates a predominant bulk contribution with a constant phase element which takes its origin from the electrode roughness. The results of CaWO4 are relevant for its applications to electro-photocatalysis. The conversion percentages of Phenobarbital reached respectively 54% and 66% with electro-catalysis and electro-photocatalysis under UV/C irradiation. The oxidation obeys to a first order kinetic with a rate constant of 1.98 × 10−3 min−1 and 2.7 × 10−3 min−1, respectively.