Photocatalytic hydrogen evolution over cyanine-sensitized Ag/TiO2

Sensitization of TiO2 by dyes such as cyanine and their derivatives is used as a technique to improve potency for the production of hydrogen gas as an alternative green fuel. These dyes shift the spectrum of TiO2 from the UV region to the visible region, enabling it to harvest as much sunlight as possible. Herein, four different derivatives of cyanine (labelled C1, C2, C3, and C4) were prepared and doped in Ag/TiO2 via the impregnation method. The properties of the prepared photocatalysts were studied by XRD, SEM-EDS, FTIR, and UV-visible spectroscopy. The sensitized photocatalysts exhibited a similar morphology, nanoscale particle size, and good absorbance in the visible region. The rate constant for the photocatalytic activity of Ag/TiO2 showed a great enhancement for hydrogen evolution after sensitization from 0.088 to 0.33 mu mol min(-1). Doping of the C2 derivative in Ag/TiO2 promoted the photocatalytic and sonophotocatalytic rates of H-2 production by 7.5 and 9 times, respectively. Also, the amount of photocatalyst had a significant effect on the photocatalytic activity of the sensitized Ag/TiO2 , where 0.14 g was the optimum dose, giving the maximum yield at both the initial rate and 300 min. One of the important factors causing the efficiency to reach high levels is the inhibition of photogenerated electron/hole recombination. This was achieved by adding a small quantity of methanol, which increased the rate by 9 times. The stability of the prepared photocatalysts was tested, which gave good results even after their 5th use. All the results confirmed that the sensitization of metal oxides is a promising solution in industry to produce dean energy (H-2) in high quantities over highly stable photocatalysts.

Automated summary

Sensitization of TiO2 using dyes shifts its spectrum to the visible region, leading to improved hydrogen production. The sensitized photocatalysts exhibited similar morphology and nanoscale particle size, with increased absorbance in the visible region. The addition of the C2 derivative in Ag/TiO2 significantly enhanced the photocatalytic and sonophotocatalytic rates of hydrogen evolution. Methanol addition inhibited photogenerated electron/hole recombination and increased the rate. The sensitization of metal oxides shows promise in industry for producing clean energy in high quantities.