Ag-decorated TiO2 nanofibers as Arrhenius equation-incompatible and effective photocatalyst for water splitting under visible light irradiation

The decoration of titanium oxide nanostructures with noble metal forming nanoparticles and a nanofibrous morphology can result in overcoming the electron-hole fast recombination problem and enhancing the activity of this important photocatalyst under the visible light irradiation spectra. In this study, Ag-decorated TiO2, with different Ag contents, was synthesized in nano-particulate and nanofibrous forms. Synthesis of Ag-decorated nanofibers was performed by calcination of titanium isopropoxide/silver nitrate/polyvinylpyrrolidone electrospun nanofiber mats at 700 degrees C. To prepare the nanoparticles, the initial electrospun sol-gel was dried, crushed and finely ground before the calcination process. As a photocatalyst for the water photosplitting process under visible light irradiation, the rate of hydrogen production was strongly affected by nanomorphology, Ag content, and reaction temperature. Typically, due to electron confinement in the OD nanostructure, the nanofibrous morphology markedly enhanced the hydrogen evolution rate, by almost 8-fold compared with the nanoparticles. The hydrogen production rates for the samples containing 1 wt% Ag were 5.5 and 120 mmol H-2/gcat for the nanoparticles and nanofibers, respectively. For both formulations, increasing the silver content led to enhancement of the hydrogen production rate; however, the influence was clearer in the case of the nanoparticles. Investigation of the photocatalysis mechanism indicated that the localized surface plasmon of the silver nanoparticles was the main parameter resulting in the observed high photocatalytic activity under visible light irradiation.