Simultaneous etching and doping of TiO2 nanowire arrays for enhanced photoelectrochemical performance.

We developed a postgrowth doping method of TiO2 nanowire arrays by a simultaneous hydrothermal etching and doping in a weakly alkaline condition. The obtained tungsten-doped TiO2 core-shell nanowires have an amorphous shell with a rough surface, in which W species are incorporated into the amorphous TiO2 shell during this simultaneous etching/regrowth step for the optimization of photoelectrochemical performance. Photoanodes made of these W-doped TiO2 core-shell nanowires show a much enhanced photocurrent density of ~1.53 mA/cm(2) at 0.23 V vs Ag/AgCl (1.23 V vs reversible hydrogen electrode), almost 225% of that of the pristine TiO2 nanowire photoanodes. The electrochemical impedance spectroscopy measurement and the density functional theory calculation demonstrate that the substantially improved performance of the dual W-doped and etched TiO2 nanowires is attributed to the enhancement of charge transfer and the increase of charge carrier density, resulting from the combination effect of etching and W-doping. This unconventional, simultaneous etching and doping of pregrown nanowires is facile and takes place under moderate conditions, and it may be extended for other dopants and host materials with increased photoelectrochemical performances.