In Situ Spatial Charge Separation of an Ir@TiO₂ Multiphase Photosystem toward Highly Efficient Photocatalytic Performance of Hydrogen Production

Abstract

This work focuses on the formation of Ir3+ dopants in the host TiO2 matrix to decrease the band gap energy and a built-in electric field at the interface between Ir0 and TiO2. X-ray diffraction results show that the anatase percentage is increased from 70 to 90% with increasing Ir doping concentration using the hydrothermal procedures at 200 °C for 24 h. X-ray photoelectron spectroscopy results demonstrate that the binding energies of Ti4+ (Ti 2p1/2 and Ti 2p3/2) shift slightly positively after Ir doping. The influence of Ir doping on the photoelectrochemical and optical properties of anatase/rutile TiO2 is characterized by linear sweep voltammetry and photoluminescence spectroscopy. These results suggest that the photoinduced electron–hole pair recombination rate is decreased in the presence of the Ir dopant. Outstanding H2 evolution reaction efficiencies of 48 and 23.5 μmol·h–1·g–1 with apparent quantum efficiency values of approximately 15.7 and 4.5% determined at 365 and 420 nm, respectively, are achieved with the 1.0% Ir/TiO2 specimen in photocatalytic systems to enhance hydrogen evolution.