Visible‐Light‐Induced Electron Transport from Small to Large Nanoparticles in Bimodal Gold Nanoparticle‐Loaded Titanium(IV) Oxide

Abstract

A key to realizing the sustainable society is to develop highly active photocatalysts for selective organic synthesis effectively using sunlight as the energy source. Recently, metal-oxide-supported gold nanoparticles (NPs) have emerged as a new type of visible-light photocatalysts driven by the excitation of localized surface plasmon resonance of Au NPs. Here we show that visible-light irradiation (λ>430 nm) of TiO2 -supported Au NPs with a bimodal size distribution (BM-Au/TiO2 ) gives rise to the long-range (>40 nm) electron transport from about 14 small (ca. 2 nm) Au NPs to one large (ca. 9 nm) Au NP through the conduction band of TiO2 . As a result of the enhancement of charge separation, BM-Au/TiO2 exhibits a high level of visible-light activity for the one-step synthesis of azobenzenes from nitrobenzenes at 25 °C with a yield greater than 95 % and a selectivity greater than 99 %, whereas unimodal Au/TiO2 (UM-Au/TiO2 ) is photocatalytically inactive.

Harvesting Lost Photons: Plasmon and Upconversion Enhanced Broadband Photocatalytic Activity in Core@Shell Microspheres Based on Lanthanide‐Doped NaYF4, TiO2, and Au

“…The high-resolution spectrum of Au4f (Figure 2 D) exhibits two peaks at 84.0 eV (Au4f 7/2 ) and 87.6 eV (Au4f 5/2 ) that can be assigned to metallic Au. [ 38,39 ] The binding energies of 459.2 and 464.9 eV, ascribed to Ti2p 3/2 and Ti2p 1/2 , respectively, are consistent with the typical values reported for TiO 2 (Figure 2 E). [ 40 ] The asymmetric profi le of the O1s band ( Figure 2 F) indicates that more than one kind of oxygen species exist.…”

Plasmonic Au Decorated Single‐crystal‐like TiO2‐NaYF4 Mesoporous Microspheres for Enhanced Broadband Photocatalysis

“…The four peaks at 84.0 eV (Au 4f 7/2 ), 87.6 eV (Au 4f 5/2 ), 353.0 eV (Au 4d 3/2 ) and 334.0 eV (Au 4d 5/2 ) can be assigned to metallic Au. [26,27] In Figure 3c, the binding energies of 458.9 eV and 464.5 eV are consistent with the typical values reported for Ti 2p 3/2 and Ti 2p 1/2 , respectively. [28] In Figure 3d, the asymmetric profile of O 1s band indicates that two kinds of oxygen species exist in the system.…”

A bi-overlayer type plasmonic photocatalyst consisting of mesoporous Au/TiO2 and CuO/SnO2 films separately coated on FTO

“…We have reported that Au/TiO 2 with a bimodal size distribution of Au nanoparticles exhibits a high level of activity for the one-step synthesis of azobenzenes from nitrobenzenes with high yield and selectivity because of the electron transport from small Au nanoparticles to large ones. 20 be frequently the rate-determining step in the photocatalytic reactions. In the preceding work, 23 we have found that the Au/mp-TiO 2 | Pt shows the highest photocatalytic activity among Au/mp-TiO 2 on various conducting substrates.…”

“…In the preceding work, 23 we have found that the Au/mp-TiO 2 | Pt shows the highest photocatalytic activity among Au/mp-TiO 2 on various conducting substrates. 23 Regardless of the high cost, Pt is usually used as the cathode of fuel cells due to 20 its excellent electrocatalyst for oxygen reduction reaction (ORR). 24 The application of the large-scale fuel cells needs the development of Pt-alternative materials with high electrocatalytic activity for ORR, low cost, and earth abundance.…”

“…15 The electrochemical properties of the CuO/mp-SnO 2 (4 cm 2 ) | FTO electrodes were measured in 0.1 M NaClO 4 aqueous solution in a regular three-electrode electrochemical cell using a galvanostat/potentiostat (HZ-5000, Hokuto Denko). Glassy carbon and a Ag/AgCl electrode (TOA-DKK) were used as a 20 counter electrode and a reference electrode, respectively.…”