Surface functionalized HTiO nanowires engineered for visible-light photoswitching, electrochemical water splitting, and photocatalysis.

This article demonstrates comprehensive studies on different visible-light driven photoelectrochemical and photocatalytic aspects of a hydrothermally synthesized n-type HTiO (HTO) nanowire mesh and its carbon and nitrogen functionalized counterparts, namely C-HTO and N-HTO. It was found that the presence of various defect states within the band gap of HTO, C-HTO and N-HTO nanowires, make them photoactive under visible-light. The photo-conversion efficiencies of HTO, C-HTO, and N-HTO nanowire electrodes are about 0.066, 0.129, and 0.076%, respectively, at around 1 V vs. Ag/AgCl. Carbon functionalization of HTO nanowires has been found to be most beneficial in increasing the charge carrier density, resulting in the highest current density, high photo conversion efficiency, remarkable photoelectrochemical water splitting performance and enhanced photocatalytic activity. The photocurrent density of the C-HTO NWs was found to be 0.0562 mA cm at 1 V vs. Ag/AgCl, which is almost two times that of the pristine HTO NWs (0.029 mA cm). Although nitrogen functionalization increases the charge carrier density of the HTO nanowires, nitrogen incorporation produces lots of recombination centres in the nanowires, which are found to play a detrimental role in the photoelectrochemical and photocatalytic performance of N-HTO nanowires, limiting the expected performance. Therefore, the present study demonstrates a suitable surface engineering technique for nanostructures to maximize the utilization of green solar light.