V and N co-doped TiO2 nanocatalysts were synthesized by a simple two-step thermal annealing process using nanotubular titanic acid precursors. The effect of the doping orders of V and N on the structural, photoelectochemical, and photocatalytic properties of TiO2 was thoroughly investigated. Co-doped TiO2 that was first doped with N via calcination in the presence of ammonia at 600 degrees C before being doped with V in air at 500 degrees C displayed improved visible light photoelectrochemical and photocatalytic properties compared to TiO2 that was first doped with V by calcination at 500 degrees C in air and then doped with N at 600 degrees C in the presence of ammonia. X-ray photoelectron spectroscopy (XPS) revealed that the sample was first introduced with N impurities, while V was incorporated into the lattice of TiO2. Only interstitial N remained after the nitridation process, and V species were present as V5+ and V4+. The interstitial N was responsible for the strong visible light absorption. Meanwhile V4+/V5+ efficiently separated photogenerated carriers and contributed to the material's visible light activity for the photocatalytic oxidation of propylene, suggesting that doping order influenced the catalytic activity of the co-doped TiO2 by determining the types of dopant ions present and their valences. (C) 2015 The Electrochemical Society.