Passivated n-p co-doping of niobium and nitrogen was successfully incorporated into self-organized TiO2 nanotube arrays by anodizing Ti-Nb alloys, followed with the heat treatment in a flow of ammonia gas. Nb was doped into TiO2 nanotube arrays during the anodization by substituting Ti4+ with Nb5+, while Nb was doped into TiO2 nanotube arrays during the heat treatment by substituting O2- with N3-. Since Nb in TiO2 enhanced the adsorption of NH3 molecules onto the nanotube arrays, Nb doping was found to promote the subsequent N doping into the anatase lattice. As predicted by first-principles band structure calculations, Nb/N co-doped titanium oxide nanotube arrays demonstrated a largely enhanced visible light response and visible light photocatalytic performance on the degradation of methylene blue, compared to TiO2 nanotube arrays or TiO2 nanotube arrays with either dopant. The passivated n-p co-doping approach may also be applied to other material systems and promise a wide range of technical applications. (C) 2013 Elsevier B.V. All rights reserved.