Hydrogen production over the hetero-junction MnO2/SiO2

Abstract

The motivation of this work is the hydrogen production as a non-polluting renewable energy under visible light. For this purpose, the hetero-junction 2%MnO2/SiO2 was synthetized by the impregnation method and characterized by X-ray diffraction, scanning electron microcopy (MEB), FTIR spectroscopy, diffuse reflectance and electrical conductivity. The X-ray analysis shows the amorphous silica substrate and the rutile phase MnO2. The optical curve (αhν)2 as a function of hν shows a direct transition of 1.83 eV for MnO2. The capacitance measurement of the rutile indicates a flat band potential of −0.027 VSCE, more negative than the hydrogen evolution in SO32− aqueous solution. As application, hydrogen was successfully evolved over the hetero-junction MnO2/SiO2. A good H2 production was obtained after 30 min of irradiation corresponding to 5.1 mmol h−1 g−1 under visible light (29 mWcm−2). The improved photocatalytic performance is due to the sensitizer MnO2 homogeneously supported on porous SiO2 substrate acting as templating agent.