Preparation and photocatalytic properties of RuO2/TiO2 composite nanotube arrays

RuO2/TiO2 composite nanotube arrays were prepared using an anodic oxidation method combined with dipping. The photocatalytic properties of RuO2/TiO2 nanotube arrays in methylene blue solution were investigated under visible light irradiation. The results showed that Ru existing in the form of RuO2 was dispersed uniformly on the surface of TiO2 nanotubes, and the RuO2 did not change the crystal structure of TiO2 nanotubes. The load of RuO2 on TiO2 had a little influence on the band-gap energy and the absorption band edge, but could increase the amount of Ti-OH functional groups on the surface of TiO2 nanotubes. The RuO2/TiO2 nanotube arrays with the optimal photocatalytic activity were formed in the ruthenium chloride solution with a concentration of 0.0030 mol/L. The 2 h photocatalytic degradation rate of methylene blue increased from 38% for pure TiO2 nanotubes to 69% for RuO2/TiO2 nanotube arrays. This work demonstrated that RuO2/TiO2 nanotube arrays showed an improved photocatalytic property over pure TiO2 nanotubes due to the fact that RuO2 could capture the photo-generated holes, which greatly decreased the recombination of the photo-generated electrons and holes, and hence lengthen the lifetime of photo-induced electrons and increased the amount of hydroxyl groups absorbed on the TiO2 nanotubes surface.