A new insight into Au/TiO2-catalyzed hydrogen production from water-methanol mixture using lamps containing simultaneous ultraviolet and visible radiation

Abstract

Different amounts of Au NPs were deposited on a modified-TiO2 using the deposition-precipitation method with urea and used for hydrogen production via water splitting at room temperature and atmospheric pressure. Methanol and simultaneous UV and visible radiation were used as sacrificial reagent and excitation sources, respectively. Both modified-support and photocatalysts were characterized by XRD, HRTEM or STEM-HAADF, FE-SEM-EDS, N2 physisorption and UV–vis DRS. The emission spectra of the excitation sources were also obtained by spectrofluorometry. XRD, HRTEM and UV–vis DRS results showed that TiO2 anatase was the predominant crystalline phase, with a relative high specific surface area. STEM-HAADF and FE-SEM-EDS techniques revealed that the average Au NPs size was increased with Au loading from 3.2 to 14.9 nm and that the estimated Au contents were close to the expected theoretical values. On the other hand, the photo-generated hydrogen was significantly increased with Au NPs incorporation and it could be associated to a slightly decrease of the energy band gap and the intrinsic localized surface plasmon resonance that can suppress the high rate of electron-hole pair recombination. The photocatalytic performance also depended on multiples experimental factors, such as: stirring speed, amount and size of Au NPs, as well as the radiation source. The highest hydrogen production rate (2336 μmol-H2/gcat⋅h) was obtained using the Au/TiO2 photocatalyst with 0.5 wt% Au, a stirring speed of 800 rpm and purple lamp (13 W) simultaneously emitting UV (52%) and visible (48%) radiation.