Photodeposition of CdSe using Se-TiO2 suspensions as photocatalysts

The photodeposition of cadmium selenide (CdSe) using Se-TiO2 photocatalysts was studied at pH 3.5 and 7 in the presence of formic acid. The Se-TiO2 photocatalysts were obtained by Se ion photoreduction using selenite (Se(IV)) and selenate (Se(VI)) as precursors. The formation of cadmium selenide was attributed to the reaction between cadmium ions and selenide ions (Se2-) released from the Se deposited on TiO2 particles under illumination. The release of the Se2- ions from the Se-TiO2 is believed to be the determining step for the formation of the CdSe particles, hence controlling their morphology as either rod-shaped or spherical. Metallic cadmium was also detected on the surface of TiO2 particles as a product of the photocatalytic reduction at pH 7. Its formation was attributed to the photoreduction of cadmium by the photogenerated electrons in the TiO2 and/or the Se semiconductors. (c) 2005 Elsevier B.V. All rights reserved.