title: Preparation, characterization and application of CuCrO2/ZnO photocatalysts for the reduction of Cr(VI).
abstract: The delafossite CuCrO2 elaborated by sol-gel from 40 nm diameter colloid is optically active in the visible region. It is characterized physically and photoelectrochemically. The microstructure is fairly homogenous with a mean crystallite size of ca. 2 microm. The optical gap (1.30 eV), determined from the diffuse reflectance, is well suited to the sunlight spectrum. The Mott Schottky plot is characteristic of P-type conductivity with a flat band potential of -0.26 V(SCE). As application, the photoreduction of chromate is successfully achieved in air-equilibrated suspension CuCrO2/ZnO (1/1). CuCrO2 is photoactivated by visible light and the electrons in the conduction band (-1.34 V(SCE)) are injected to ZnO. In the presence of salicylic acid, a conversion of Cr(VI) to Cr(III) of 57% is obtained under optimal conditions (pH 3 at 25 degrees C, 5 x 10(-4) mol/L) because of the HCrO4- dark adsorption onto ZnO (4HCrO4- + 3C7H6O3 + 18O2 + 16H+ --> 4Cr3+ + 21CO2 + 19H2O, deltaG0 = -557 kcal/mol). Prolonged illumination is accompanied by a deceleration in the photoactivity owing to the competitive water reduction, an issue of energetic concern. The hetero-system exhibits self sensitization for hydrogen production with an evolution rate of 149 micromol/(hr x g).
authors.affiliation: Technical and Scientific Research Centre of Physico-Chemical Analysis, BP 248, RP 16004, Algiers, Algeria.
authors.forename: Wahiba
authors.initials: W
authors.lastname: Ketir
authors.forename: Gharib
authors.initials: G
authors.lastname: Rekhila
authors.forename: Mohamed
authors.initials: M
authors.lastname: Trari
authors.forename: Abdelatif
authors.initials: A
authors.lastname: Amrane
mesh_terms: D002384:Catalysis; D002857:Chromium / Q000737:chemistry* / Q000528:radiation effects; D003300:Copper / Q000737:chemistry* / Q000528:radiation effects; D008903:Minerals / Q000737:chemistry*; D010084:Oxidation-Reduction; D015034:Zinc Oxide / Q000737:chemistry
chemical_list: D008903:Minerals; D002857:Chromium; D003300:Copper; D015034:Zinc Oxide