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

Abstract

In this paper, highly ordered <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm TiO}_{2}$</tex></formula> 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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm TiO}_{2}$</tex></formula> nanotube arrays is affected by the two-step anodization process and the polar solvent containing electrolytes. With two-step anodization, the surface morphology of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm TiO}_{2}$</tex></formula> nanotube arrays is orderly and uniform. Moreover, the pore diameter is stupendously homogeneous. The structural parameters of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm TiO}_{2}$</tex></formula> 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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm TiO}_{2}$</tex> </formula> nanotube arrays were analyzed by measuring its electric resistance response in different <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm H}_{2}$</tex></formula> concentrations. The results demonstrate that <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm TiO}_{2}$</tex></formula> nanotube arrays have high hydrogen sensitivity at room temperature.