Abstract
The fabrication of small anatase titanium dioxide (TiO2) nanoparticles (NPs) attached to larger anisotropic gold (Au) morphologies by a very fast and simple two-step microwave-assisted synthesis is presented. The TiO2/Au NPs are synthesized using polyvinylpyrrolidone (PVP) as reducing, capping and stabilizing agent through a polyol approach. To optimize the contact between the titania and the gold and facilitate electron transfer, the PVP is removed by calcination at mild temperatures. The nanocatalysts activity is then evaluated in the photocatalytic production of hydrogen from water/ethanol mixtures in gas-phase at ambient temperature. A maximum value of 5.3 mmol·h−1 (7.4 mmol·h−1) of hydrogen is recorded for the system with larger gold particles at an optimum calcination temperature of 450°C. Herein we demonstrate that TiO2-based photocatalysts with high Au loading and large Au particle size (≈50 nm) NPs have photocatalytic activity.
Highlights
The prospect of achieving clean and renewable hydrogen at ambient temperatures through the photocatalytic water splitting reaction has gained much attention since the pioneer work of Honda and Fujishima in 1972 using TiO2 as photocatalyst in a photoelectrochemical cell (Fujishima and Honda, 1972)
Anhydrous benzyl alcohol (99%) and pure ethanol (> 99.9%) was purchased from Scharlau, and ethylene glycol (EG ≥ 99%), HCl (37%) and acetone were purchased at Panreac
The TiO2 NPs are formed by sol-gel synthesis in a microwave oven using titanium butoxide (TBOT) as precursor, benzyl alcohol (BA) as solvent, and polyvinylpyrrolidone (PVP) as stabilizer
Summary
The prospect of achieving clean and renewable hydrogen at ambient temperatures through the photocatalytic water splitting reaction has gained much attention since the pioneer work of Honda and Fujishima in 1972 using TiO2 as photocatalyst in a photoelectrochemical cell (Fujishima and Honda, 1972). Noble metal NPs, such as Au (Bamwenda et al, 1995; Primo et al, 2011; Jovic et al, 2013a,b; Taboada et al, 2014a,b), Pd (Khojasteh et al, 2016), Pt (Jovic et al, 2013b; Al-Azri et al, 2015), Au-Cu (Bonmatí et al, 2015), Au-Pd (Su et al, 2014), or metal oxide NPs, like RuO2 or CuO (Bandara et al, 2005; Xu and Sun, 2009; Yu et al, 2011) have been used These doping agents act as a cocatalyst, enhancing the electron-hole charge separation, TiO2/Au Nanoparticles for Hydrogen Generation avoiding or delaying the recombination rate and increasing the overall photocatalytic activity. This technology is still not fully commercially available, mainly due to the low efficiency of the materials, to their low stability during the water splitting reaction, and to its overall high cost
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