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 microstrncture is fairly homogenous wi...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 microstrncture is fairly homogenous with a mean crystallite size of ca. 2 Ixm. 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 VscE. 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 VscE） 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~C, 5x 10-4 mol/L） because of the HCrO4- dark adsorption onto ZnO （4HCrO4- ＋ 3C7H603 ＋ 1802 ＋ 16H~ 4Cr3＋ ＋ 21CO2 ＋ 19H20, AGO = -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 Ixmol/（hr.g）.展开更多
基金Financial support of this investigation by the faculty of chemistry
文摘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 microstrncture is fairly homogenous with a mean crystallite size of ca. 2 Ixm. 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 VscE. 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 VscE） 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~C, 5x 10-4 mol/L） because of the HCrO4- dark adsorption onto ZnO （4HCrO4- ＋ 3C7H603 ＋ 1802 ＋ 16H~ 4Cr3＋ ＋ 21CO2 ＋ 19H20, AGO = -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 Ixmol/（hr.g）.
