Au-TiO₂Nanocomposites and Efficient Photocatalytic Hydrogen Production under UV-Visible and Visible Light Illuminations: A Comparison of Different Crystalline Forms of TiO₂

Abstract

Au (∼1 wt%) /TiO 2(anatase or rutile or P25) nanocomposites were prepared by the solvated metal atom dispersion (SMAD) method, and the as-prepared samples were characterized by diffuse reflectance UV-visible spectroscopy, powder XRD, BET surface analysis measurements, and transmission electron microscopy bright field imaging. The particle size of the embedded Au nanoparticles ranged from 1 to 10 nm. These Au/TiO 2 nanocomposites were used for photocatalytic hydrogen production in the presence of a sacrificial electron donor like ethanol or methanol under UV-visible and visible light illumination. These nanocomposites showed very good photocatalytic activity toward hydrogen production under UV-visible conditions, whereas under visible light illumination, there was considerably less hydrogen produced. Au/P25 gave a hydrogen evolution rate of 1600 mol/h in the presence of ethanol (5 volume %) under UV-visible illumination. In the case of Au/TiO 2 prepared by the SMAD method, the presence of Au nanoparticles serves two purposes: as an electron sink gathering electrons from the conduction band (CB) of TiO 2 and as a reactive site for water/ethanol reduction to generate hydrogen gas. We also observed hydrogen production by water splitting in the absence of a sacrificial electron donor using Au/TiO 2 nanocomposites under UV-visible illumination.

Efficient Degradation of Methylene Blue over Two‐Dimensional Au/TiO2 Nanosheet Films with Overlapped Light Harvesting Nanostructures

“…Although much work has been done to investigate LSPRenhanced photocatalysis, the enhancement mechanism is still under debate. Jose et al observed that the localized electric field created by Au NPs could not induce charge carriers in the near-surface region of TiO 2 , because the LSPRabsorption of Au NPs does not overlap with the TiO 2 absorption [40]. The LSPR-absorption band of Au NPs is usually larger than 500 nm, and the overlap between the absorption of TiO 2 and LSPR-absorption of Au NPs is very weak, leading to a relative poor photocatalytic activity.…”

Photocatalytic removal of methyl orange using Ag/Zn–TiO2nanoparticles prepared by different methods

“…Furthermore, higher degradation efficiency of sol-gel-derived nanoparticles could be related to larger surface area and total pore volume compared to another sample. Large specific surface area allows more dyes to be absorbed onto the surface of Ag/Zn-TiO 2 nanoparticles, while high pore volume (mesopores) allows fast diffusion of different liquid reactants and products during the photocatalytic reaction, which can enhance the rate of photocatalytic degradation [34,35]. The results revealed that the sol-gel method for preparation of TiO 2 nanoparticles can produce photocatalyst with better activity.…”

Synthesis and Characterization of Au@TiO₂ NWs and their Catalytic Activity by Water Splitting: A Comparative Study with Degussa P25

“…Some of the chemical modifications include the doping of TiO 2 with metal and nonmetallic elements (Stroyuk et al, 2009;Primo et al, 2011;Kudo and Miseki, 2008;Ortega et al, 2014;Yuzawa et al, 2012;Tanaka et al, 2012;Padikkaparambil et al, 2013). The incorporation of noble metals, such as platinum (Pt), gold (Au) and silver (Ag), on the surface of titanium oxide, has been gaining a lot of interest in recent years due to the ability of the noble metal nanoparticles in reducing the fast recombination of the photogenerated charge carriers, enabling the use of visible light (Fang et al, 2012;Naseri et al, 2011;Lakshminarasimhan et al, 2007;Jose et al, 2013;Naldoni et al, 2013;Chen et al, 2011). By reducing the photogenerated charge carriers, the UV activity is increased due to the electron transfer from the Conduction Band (CB) of TiO 2 to the noble metal nanoparticles (Chen et al, 2011).…”

“…By reducing the photogenerated charge carriers, the UV activity is increased due to the electron transfer from the Conduction Band (CB) of TiO 2 to the noble metal nanoparticles (Chen et al, 2011). The photoactivity in the visible range of the electromagnetic spectrum can be explained due to the surface plasmon resonance effect and charge separation by the transfer of photoexcited electrons from the metal nanoparticles to the CB of TiO 2 (Jose et al, 2013;Naldoni et al, 2013;Chen et al, 2011;Gomes-Silva et al, 2011;Murdoch et al, 2011;Baatz et al, 2008;Oros-Ruiz et al, 2013).…”