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The delafossite CuCrO2 elaborated by sol-gel from 40nm 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.2μm.The optical gap(1.30eV),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-0.26VSCE.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(-1.34VSCE)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(pH3 at 25°C,5×10-4mol/L)because of the HCrO4 dark adsorption onto ZnO(4HCrO4-+3C7H6O3+18O2+16H+→4Cr3++21CO2+19H2O,△G0 =-557kcal/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 149μmol/(hr·g).
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 μm. 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 -0.26VSCE.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 electron in the conduction band (-1.34VSCE) are injected to ZnO. The presence of salicylic acid, a conversion of Cr (VI) to Cr (III ) of of 57% obtained under optimal conditions (pH3 at 25 ° C, 5 × 10-4mol / L) because of the HCrO4 dark adsorption onto ZnO (4HCrO4- + 3C7H6O3 + 18O2 + 16H + → 4Cr3 ++ 21CO2 + 19H2O, △ G0 = -557 kcal / mol) .Prolonged illumination is accompanied by a deceleration in th e 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 μmol / (hr · g).