A NiO/TiO₂ junction electrode constructed using self-organized TiO₂ nanotube arrays for highly efficient photoelectrocatalytic visible light activations

Abstract

One dimensional (1D), self-organized TiO 2 nanotube arrays are known to have excellent charge transport properties and a NiO/TiO 2 junction is efficient in separating electron–hole pairs. This paper describes the synthesis of a NiO/TiO 2 junction electrode constructed using self-organized TiO 2 nanotube arrays combining the above two properties. The self-organized TiO 2 nanotube arrays used in this study were prepared by anodizing titanium films, which resulted in closely packed n-type TiO 2 tubes with an inner pore diameter of 60–90 nm, a wall thickness of approximately 15 nm and a length of 600 nm. The NiO/TiO 2 junction was synthesized by electroless plating and annealing which resulted in TiO 2 nanotube arrays coated with a layer (about 200 nm in thickness) of NiO particles (20–40 nm). The resulting NiO/TiO 2 junction electrode enabled us to obtain an enhanced photocurrent (3.05 mA cm −2 ) as compared with a TiO 2 electrode based on TiO 2 nanotube arrays (0.92 mA cm −2 ) under AM 1.5 G (100 mw cm −2 ) at a bias of 0.65 V.