N–TiO2 crystal seeds incorporated in amorphous matrix for enhanced solar hydrogen generation: Experimental & first-principles analysis

Abstract

We present here a combined study on the photoelectrochemical activity of highly active Nitrogen doped titanium dioxide thin-film using experiments and First principle density (DFT) based calculation. Hybridization of N 2p with O 2p and localized valence band upshifting leads to the reduction in band-gap of N–TiO2. To validate theoretical findings, the role of nitrogen in TiO2 is revisited with a focus on partial crystallinity. The best-case photoelectrode, nanostructured partially crystalline nitrogen-doped titanium dioxide (PCNDTO) offered photocurrent density of 24.3 mA/cm2 at 1 V versus saturated calomel electrode (SCE). The absence of well-defined peaks and long-range order in XRD pattern and Raman spectrum respectively suggests partially crystallinity. High-resolution transmission electron microscopy (HR-TEM) images confirm the presence of TiO2 crystals in the amorphous matrix. High photoelectrochemical response can be attributed to the abundance of hydroxyl groups, high electrochemical active surface area, reduced charge transfer resistance, and reduced charge carrier recombination rate.