Defect-related light absorption, photoluminiscence and photocatalytic activity of SiO2 with tubular morphology

Abstract The research describes the synthesis, optical, photocatalytic, electrochemical and photoelectrocatalytical properties of highly defected, low surface area, tubular SiO 2 . High surface density of light-absorbing defects is obtained by conducting the synthesis at low temperature (0 °C) and by optimizing the ratios between reactants. The calcined tubular SiO 2 is characterized by intense and broad absorption band centered at ≈320 nm, spanning from deep UV to green. The formation of Si 3+ surface defects by calcination is accompanied by a substantial intensification of light absorbing characteristics. The annealing leads also to appearance of intense photoluminescence bands centered at around 433 and 533 nm for excitation wavelengths 320–380 nm. The photocatalytic generation of H 2 and CO 2 from water-methanol mixture under solar (AM 1.5) and visible (λ>390 nm) irradiation is performed to probe the capability of light-absorbing defects of SiO 2 to work as active sites and to gather indirect information on nature of active sites. The electrochemical and photoelectrochemical activity of tubular SiO 2 are highlighted by employing [Ru(bpy) 3 ]Cl 2 complex as electron transfer witness. According to our results, highly defected nanotubular SiO 2 exhibit uncommon optical, light harvesting, electronic and electrochemical properties with great potential for practical applications in numerous fields.