Photocatalytic water splitting for hydrogen production under visible light on Ir and Co ionized titania nanotube

Highly dispersed iridium and cobalt metal particles (average 3 nm) were introduced in the texture of the synthesized titania nanotube (TiNT) by ion-exchange method, which were found to be effective photocatalysts for the production of stoichiometric hydrogen and oxygen by the splitting of water under the visible light irradiation. Thus prepared Ir(IE)/TiNT and Co(IE)/TiNT catalysts evolved hydrogen at the rate of 7.05 μmol/h/0.5 g and 1.27 μmol/h/0.5 g in aqueous methanol and 2.73 μmol/h/0.5 g and 0.67 μmol/h/0.5 g in pure water, respectively. The band gap energies were decreased to 2.5 eV and 2.6 eV from 3.1 eV of bare TiNT by introducing highly dispersed Ir and Co nanoparticles in the texture of TiNT, respectively, resulting in the improved photo-response towards visible light. However, visible light photo-activity for water splitting was not observed on the large aggregated Ir and Co particles on TiNT prepared by impregnation method. The prepared catalysts were characterized by FE-SEM, HR-TEM, SEMEDX, XRD, UV–vis DRS spectra, photocurrent density and BET surface area.