Nitrogen doped anodic TiO2 nanotubes grown from nitrogen-containing Ti alloys

N-doped TiO2 nanotubes were produced by anodization of a TiN alloy. The alloy was prepared to contain approximately 5 at.% of N from high-purity Ti and TiN powders using an arc-melting and consisted of a two-phase structure with different N-contents. Anodization of the alloy in fluoride-containing electrolyte results, under optimized conditions, in the growth of an ordered TiO2 nanotube layer on both phases. On the N-rich phase significantly smaller nanotubes are grown while on the low N-concentration phase nanotubes with larger diameter were formed. However, XPS and photoelectrochemical measurements demonstrate successful nitrogen doping of the resulting nanotube layers, which leads to a significant visible photoresponse from this material.