The effect of doping of TiO₂ thin films with low-energy O²⁺ ions on increasing the efficiency of hydrogen evolution in photocatalytic reactions of water splitting

The aim of this research work is to evaluate the efficiency and prospects of using low-energy O²⁺ ion beams with an energy of 40 keV and irradiation fluences of 10¹⁴–5 × 10¹⁵ ion/cm² to increase the photocatalytic activity of thin films based on TiO₂. As research methods, methods of atomic force microscopy, energy-dispersive analysis, X-ray diffraction and UV–Vis spectroscopy were applied. According to the obtained data on changes in surface morphology as a result of irradiation, the main changes are associated with the formation of chillocks on the surface at doses of 10¹⁴–10¹⁵ ion/cm², followed by an increase in the size and density of chillocks, and for samples irradiated with a dose of 5 × 10¹⁵ ions/cm², the emergence of wavy formations on the surface associated with reorientation of grains and structural disordering is observed. As shown by the results of X-ray data, the main structural changes in the irradiated films are associated with partial fragmentation of grains and their subsequent reorientation at high radiation doses. In the case of irradiated samples, a decrease in the band gap is observed, which is caused by a change in the electron density as a result of irradiation. The results of the photochemical decomposition of water and the production of hydrogen showed that the use of modified thin films led to an increase in the rate of hydrogen production by 5.4–8 times, depending on the irradiation dose of the samples.