Understanding Photocatalytic Metallization of Preadsorbed Ionic Gold on Titania, Ceria, and Zirconia

Abstract

A nonaqueous photodeposition procedure for forming Au nanoparticles on semiconducting supports (TiO(2), CeO(2), and ZrO(2)) was investigated. Intrinsic excitation of the support was sufficient to induce Au(0) nucleation, without the need for an organic hole-scavenging species. Photoreduction rates were higher over TiO(2) and ZrO(2) than over CeO(2), likely due to a lower rate of photogenerated electron recombination. Illumination resulted in metallization of the adsorbed Au species and formation of crystalline Au nanoparticles dispersed across the oxide surfaces. On the basis of transmission electron microscopy (TEM) evidence of a strong Au particle-metal oxide interaction, it is proposed that Au deposit formation proceeds via the nucleation of highly dispersed clusters which can diffuse and amalgamate at room temperature to form larger surface-defect-immobilized clusters, with the final particle size being significantly smaller than that achieved by conventional aqueous photodeposition. From this work, it is possible to draw several new fundamental insights, with regards to both the nonaqueous photodeposition process and the general mechanism by which dispersed metallic Au nanoparticles are formed from ionic precursors adsorbed upon metal oxide supports.

A Novel Structural Design of a Pt/C‐CeO2 Catalyst with Improved Performance for Methanol Electro‐Oxidation by β‐Cyclodextrin Carbonization

“…[ 7 , 9-13 ] Aiming at the CO poisoning issues, the most widely accepted strategy is to develop Pt-based alloys such as Pt-Sn, [14][15][16][17][18][19][20] Pt-Ni, [21][22][23] or Pt/ metal oxide composite catalysts such as Pt-TiO 2 [24][25][26] based on the bifunctional mechanism and the electronic effect, [27][28][29][30][31] and the latter is also related to other factors including the size and shape of metal oxide nanocrystals, the surface areas, and the support effect. [32][33][34][35] Among various possible metal oxide supports, cerium oxides (CeO 2 ) are of particular interest due to higher oxygen storage capacity and much lower price, as well as the good mechanical resistance and anticorrosion ability in acidic media, which may signifi cantly promote methanol oxidation and reduce the catalyst preparation cost. Therefore, to explore the possibility of employing CeO 2 as a co-catalyst in methanol electro-oxidation is very necessary and meaningful.…”

Physico-Chemical Effects on the Scale-Up of Ag Photodeposition on TiO2 Nanoparticles

“…Most of the methods published for the preparation of metal-decorated TiO 2 by photodeposition involve suspended particles in aqueous media [35][36][37][38][39][40][41][42][43][44][45], although non-aqueous methods have recently been reported [46,47]. Our approach for the scaleup process was different, and was developed based on sample preparation for metal photodeposition on microscope grids as discussed in the previous study [34].…”

Spectroscopic characterization of gold supported on tungstated zirconia

“…2, spectra (b)). The broad absorption with maximum at 550 nm observed on the gold-containing samples is characteristic of the plasmonic oscillation mode of nanosized gold particles [11,31,32]. The strong band at 270-293 nm has disappeared and weak signals at 225-230 and 260-275 nm are observed instead.…”