Experimental and Theoretical Insights into Influence of Hydrogen and Nitrogen Plasma on the Water Splitting Performance of ALD Grown TiO₂ Thin Films

Specific effects of hydrogen and nitrogen plasma treatment on anatase TiO₂ photoanodes, grown via atomic layer deposition (ALD), and their respective impact on water splitting properties are reported. ALD grown TiO₂ samples were exposed to reactive hydrogen and nitrogen plasmas and the photoelectrochemical efficiency of the modified samples were comparatively analyzed. Both H₂ and N₂ plasma treatment enhanced the photocurrent values compared to pristine TiO₂. Electron density at oxygen vacancy sites was decreased upon nitrogen incorporation, reflected in band gap modulation and decreased recombination probability as confirmed by spectral data. Surface modification via H₂ plasma induce more midgap states to augment the photoinduced charge carriers concentration that was supported by theoretical investigation performed on the electronic properties of both H- and N-doped TiO₂ (anatase). First-principles calculations based on Hartree-Fock-Density Functional Theory (HF-DFT) hybrid models showed good agreement with the experimental findings and confirmed electronic band gap reduction due to extra electron density introduced via H and N incorporation in TiO₂. (Chemical Equation Presented).