Nitrogen and transition-metal codoped titania nanotube arrays for visible-light-sensitive photoelectrochemical water oxidationElectronic supplementary information (ESI) available. See DOI: 10.1039/c4cc02571g

Vertically aligned titanium dioxide nanotube (TNT) arrays codoped with nitrogen and 3d transition metals were successfully fabricated using anodization and nitridation processes. The codoping of N and Fe yielded the highest visible-light-induced photoelectrochemical water oxidation due to bandgap narrowing of impurity levels by N and Fe. Vertically aligned titanium dioxide nanotube (TNT) arrays codoped with N and 3d transition metals exhibited a significant enhancement in photoelectrochemical water oxidation activity under visible-light irradiation.