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.