Isoelectric point-controlled preferential photodeposition of platinum on Cu2O-TiO2 composite surfaces

Photodeposition emerges as a convenient method to synthesize metal particles on semiconductor supports. In this work, we study the photodeposition of Pt on Cu2O-TiO2 composite surfaces employing H2PtCl6 aqueous solution as the precursor and reveal a key role of isoelectric point of oxide surfaces on the Pt photodeposition process. Under the photodeposition conditions, Pt metal particles are facilely photodeposited on TiO2 support; on Cu2O-TiO2 composite supports, the Cu2O surface is positively charged and enriched with photo-excited holes while the TiO2 surface is negatively charged and enriched with photo-excited electrons. This lead to the preferential adsorption of PtCl62- anion precursor on the Cu2O surface of Cu2O-TiO2 composite and the dominant formation of Pt oxide particles on Cu2O surface but few Pt metal particles on TiO2 surface. Consequently, the activity of resulting Pt/Cu2O-TiO2 composite photocatalysts in photocatalytic water reduction decreases as the Cu2O content increases. These results deepen the understanding of photodeposition processes on oxide composite surfaces. (C) 2019 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.