Abstract
In this work, hierarchically ordered tubular TiO2 electrodes are prepared by a simple electrochemical anodization process. Their potential application as an efficient bifunctional electrocatalyst for oxygen and hydrogen evolution reactions in neutral medium is demonstrated. The dimensions of porous tubular structures can be tuned by altering the composition of electrolyte, time of anodization, and applied voltage. Surface morphological analysis and structural characterizations are carried out by means of SEM, TEM, AFM, and XRD studies. The precise band-gap value of these electrodes is determined from diffuse reflectance UV/Vis spectroscopic studies by using the Kubelka-Munk function. These studies also reveal that the wavelength of absorption of light by nanotubular TiO2 electrodes can be extended without the addition of any dopants or sensitizers by simply tuning the parameters of the anodization process. SEM, TEM, and AFM analyses show the formation of homogeneous, porous nanotubular structures with uniform dimensions for anodized titanium plates. XRD studies confirm the formation of the anatase phase of TiO2 when the anodized samples are post-heated at a temperature of about 450 degrees C and above.