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

Abstract Photodeposition emerges as a convenient method to synthesize metal particles on semiconductor supports. In this work, we study the photodeposition of Pt on Cu 2 O-TiO 2 composite surfaces employing H 2 PtCl 6 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 TiO 2 support; on Cu 2 O-TiO 2 composite supports, the Cu 2 O surface is positively charged and enriched with photo-excited holes while the TiO 2 surface is negatively charged and enriched with photo-excited electrons. This lead to the preferential adsorption of PtCl 6 2− anion precursor on the Cu 2 O surface of Cu 2 O-TiO 2 composite and the dominant formation of Pt oxide particles on Cu 2 O surface but few Pt metal particles on TiO 2 surface. Consequently, the activity of resulting Pt/Cu 2 O-TiO 2 composite photocatalysts in photocatalytic water reduction decreases as the Cu 2 O content increases. These results deepen the understanding of photodeposition processes on oxide composite surfaces.