Anodic Fabrication of Highly Ordered ${\rm TiO}_{2}$ Nanotube Arrays and Its Hydrogen Sensing

In this paper, highly ordered ${\rm TiO}_{2}$ nanotube arrays are fabricated via electrochemical anodization of high purity Ti foil in fluorine containing electrolytes. The field emission scanning electron microscopy measurements show that the morphology of ${\rm TiO}_{2}$ nanotube arrays is affected by the two-step anodization process and the polar solvent containing electrolytes. With two-step anodization, the surface morphology of ${\rm TiO}_{2}$ nanotube arrays is orderly and uniform. Moreover, the pore diameter is stupendously homogeneous. The structural parameters of ${\rm TiO}_{2}$ nanotube arrays were improved by the addition of polar solvent, water, to electrolytes. After annealing treatment and Pd nanoparticle doping, the hydrogen sensing characteristics of ${\rm TiO}_{2}$ nanotube arrays were analyzed by measuring its electric resistance response in different ${\rm H}_{2}$ concentrations. The results demonstrate that ${\rm TiO}_{2}$ nanotube arrays have high hydrogen sensitivity at room temperature.