Rapid hydrogenation of amorphous TiO2 to produce efficient H-doped anatase for photocatalytic water splitting

Abstract

Hydrogen-doped anatase titanium dioxide (H:TiO2) thin films were synthesized by a mild annealing in hydrogen atmosphere of amorphous TiO2 thin films deposited on ITO by RF-magnetron sputtering. Two kinds of TiO2 electrodes (amorphous and anatase) were tested for the H-doping in different annealing conditions, but H-doped anatase was obtained exclusively by a rapid heat treatment in hydrogen atmosphere of amorphous TiO2 at 300°C. Instead, anatase thin films required enforced annealing conditions to incorporate H, leading to an undesirable conversion to rutile. XPS analysis reveals that in H-doped anatase thin films H atoms are bonded to O. DFT calculations, performed to investigate the density of states, predict a slight band-gap narrowing, in agreement with spectroscopic evidence. Photoelectrochemical measurements on H:TiO2 showed an elevated current density of 0.99mA/cm2 at 1.23V vs. RHE in oxygen evolution reaction, revealing better performance than pure anatase TiO2. This enhancement in catalytic activity is accounted to the effect of dangling bonds passivation performed by highly reactive H atoms, which reduce the density of carrier recombination centers. The used method for the conversion of amorphous TiO2 thin film in H:doped anatase TiO2 can be extended to amorphous TiO2 prepared by various techniques.