Laser induced H2 production employing Pt-TiO2 photocatalysts

Abstract

The photocatalytic production of hydrogen from water as well as from an aqueous methanol solution employing pre-treated TiO2 and various Pt-TiO2 photocatalysts was studied by using an Nd:YAG laser as irradiation source. The photocatalysts (0.5, 1.0, 1.5 and 2.0 wt% Pt-TiO2) were prepared by utilizing a photocatalytic reduction method upon which characterization by TEM and EDX were conducted. EDX indicated that the loading method was successful and TEM analysis confirmed the presence of Pt on the surface of TiO2 with a particle/cluster size between 11 nm and 22 nm. The impact of the loaded Pt on the band gaps of the different photocatalysts was investigated by diffuse reflectance spectroscopy (DRS) and calculated by means of the Kubelka–Munk method. The band gap values shifted sequentially from 3.236 to 3.100 eV as the loading increased. The amount of H2 produced from the individual photocatalysts dispersed in both pure water and aqueous methanol solutions, was measured manually with a gas chromatograph. As soon as irradiation was initiated, a distinct color change from shades of gray to dark blue-gray was observed for all the photocatalysts. XRD confirmed that this was due to the part conversion of the anatase phase to the rutile phase. No H2 was detected for the various photocatalysts suspended in water, i.e. in the absence of methanol. The amount of H2 produced from the various Pt photocatalysts suspended in the aqueous methanol solution was found to be the highest for the 0.5 wt% and 1.5 wt% Pt-TiO2 photocatalysts and the lowest for the 2 wt% Pt-TiO2.