Codoping titanium dioxide nanowires with tungsten and carbon for enhanced photoelectrochemical performance

Recent density-functional theory calculations suggest that codoping TiO 2 with donor-acceptor pairs is more effective than monodoping for improving photoelectrochemical water-splitting performance because codoping can reduce charge recombination, improve material quality, enhance light absorption and increase solubility limits of dopants. Here we report a novel ex-situ method to codope TiO₂ with tungsten and carbon (W, C) by sequentially annealing W-precursor-coated TiO₂ nanowires in flame and carbon monoxide gas. The unique advantages of flame annealing are that the high temperature (>1,000°C) and fast heating rate of flame enable rapid diffusion of W into TiO₂ without damaging the nanowire morphology and crystallinity. This is the first experimental demonstration that codoped TiO₂:(W, C) nanowires outperform monodoped TiO₂:W and TiO₂:C and double the saturation photocurrent of undoped TiO₂ for photoelectrochemical water splitting. Such significant performance enhancement originates from a greatly improved electrical conductivity and activity for oxygen-evolution reaction due to the synergistic effects of codoping.