Preparation of multiple-doped TiO2 nanotube arrays with nitrogen, carbon and nickel with enhanced visible light photoelectrochemical activity via single-step anodization

• Published in: International journal of hydrogen energy 2015-09, Vol.40 (36), p.12239-12252
• Main Authors: Mollavali, Majid, Falamaki, Cavus, Rohani, Sohrab
• Format: Article
• Language: English
• Subjects: Carbon; Multiple-doping; Nickel; Nitrogen; Photocatalytic property; TiO2 nanotube arrays
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2015.07.069

The main objective of this research is to enhance the photocatalytic activity of TiO2 nanotube aligned arrays (TNAs) for the visible light by multiple-doping with nitrogen, nickel and carbon for the first time. This has been achieved through anodization of titanium foils in ethylene glycol based electrolytes containing NH4F and various concentrations of K2[Ni(CN)4]. The method proposed allows for a simple one-step multiple-doping of TNAs during its electrochemical formation. The surface morphology, structure and composition of undoped and Ni–N–C-doped TNAs were investigated by field emission scanning electron microscopy (FESEM), XRD, XPS and EDX. The characterization results indicate that Ni, N and C atoms have been incorporated into the lattice of the TiO2 nanotubes. UV–Vis DRS spectroscopy and photo-electrochemical measurements showed that multiple-doping results in the broadening of the absorption region of visible light and the reduction of bandgap energy. Accordingly, multiple-doping of TNAs improves photogenerated electron–hole separation and increases transfer rate of surface charge carriers from the interior to the surface of semiconductors. Under the visible-light irradiation, the average photocurrent density of the optimal multiple-doped TNAs is 10 times greater than that of the undoped TNAs tested under the same conditions. Accordingly, Ni–C–N-doped TNAs may be considered as a promising photocatalytic material for various potential applications like water splitting under sunlight irradiation for hydrogen generation. [Display omitted] •Multiple doped TiO2 nanotubes aligned arrays have been produced.•TiO2 nanotubes are doped simultaneously with N, C and Ni atoms for the first time.•One step anodization is performed using K2[Ni(CN)4] as main source of three dopants.•Multiple-doping highly increases Vis. light absorption and reduces bandgap energy.•Photocurrent density under Vis. light may be increased up to ten times upon doping.