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

• ITO/TiO2 heterostructures were deposited by RF-magnetron sputtering.
• Mild annealing in H2 atmosphere converts amorphous TiO2 into H-doped anatase.
• H atoms formed hydroxyl groups passivating dangling bonds.
• DFT calculations endorsed experimental results.
• H:TiO2 showed enhanced photocatalytic activity.

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 0.99 mA/cm2 at 1.23 V 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.

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