Relationship between N-doping induced point defects by annealing in ammonia and enhanced thermal stability for anodized titania nanotube arrays

► Highly ordered N-doped anatase NTs with enhanced thermal stability was prepared. ► A significantly enhanced visible absorption was observed. ► Titanium interstitials play a key role in retarding A to R phase transformation. ► Titanium interstitials result in the enhanced thermal stability of anatase NTs.