Efficient Charge Separation of In‐Situ Nb‐Doped TiO 2 Nanowires for Photoelectrochemical Water–splitting

One‐dimensional TiO 2 nanowire is the top‐performing semiconductor among photoanodes for photoelectrochemical water splitting, but still limited to a fraction of the theoretically photocurrent because of modest charge transport and low charge separation properties. Here, we demonstrate high‐crystallized nanowires of Nb‐doped rutile TiO 2 for significantly increasing electron carrier density through a convenient method. The optimized Nb‐doped TiO 2 nanowires (0.5 mol% in the Nb/Ti ratio) yield a high value of charge separation efficiency (η sep ) of 97.39% at 1.23 V RHE , which is about 3 times as much as that of pristine sample (33.61% at 1.23 V RHE ). Moreover, the photoanode of Nb‐doped TiO 2 nanowires can achieve high charge transfer efficiency (η trans ) (91.07% at 1.23 V RHE ) without any oxygen evolution reaction catalysts. These results indicate that through appropriate amount of Nb doping can move the performance of TiO 2 nanowires to their theoretical potential.