Controlled synthesis and enhanced photoelectro-catalytic activity of a 3D TiO2 nanotube array/TiO2 nanoparticle heterojunction using a combined dielectrophoresis/sol–gel method

Abstract

The surface morphology, particle size and crystal structure have a great impact on the performance of materials. Therefore, it is necessary to explore a method for the controllable synthesis of materials. In this study, three-dimensional TiO₂ nanotube arrays (3D-TNAs) formed by electrochemical anodization over Ti meshes have been prepared. The TiO₂ nanotubes are oriented in all directions, and could harvest the incident light from any direction. 3D TiO₂ nanotube arrays decorated by TiO₂ nanoparticles (3D-TNAs/TiO₂) were successfully prepared by a combined dielectrophoresis (DEP)/sol–gel process. This method greatly shortens the time required for 3D-TNAs/TiO₂ preparation while increasing the density of electrode materials and particle size uniformity. Experimental results show that the morphology and size of 3D-TNAs/TiO₂ can be controlled using DEP technology. These mesh electrodes with an anatase/rutile heterojunction were applied in photoelectrocatalytic degradation of methylene blue (MB), and show a significant improvement in photoelectrocatalytic activity compared to unmodified 3D-TNAs and 3D-TNAs/TiO₂ fabricated through only a sol–gel process. The photocurrent density could reach 0.11 mA cm⁻². The superior photoelectrocatalytic activity and the photocurrent response of 3D-TNAs/TiO₂ were mainly attributed to the high specific surface area, strong light absorption, low electron–hole recombination rate and wide light-response range.