| Photo electrochemical (PEC) behavior of various nanostructured configurations of titanium dioxide were studied in the presence of coherent light and relevant comparisons were made. Ordered, nanostructured oxide layers like nanotubes, nanoparticles and planar thin films were grown on stamps of titanium metal foil by a simple electrochemical anodization process using ethylene glycol, sodium phosphate and glycerol based solutions. Moderate temperature annealing in the range of 500--600°C resulted in highly ordered structures, free from salt deposits on the surface. The PEC behavior of smooth and ribbed nanotubes was also studied. Anodic nanostructured TiO2 was noted to be highly photoactive in the presence of coherent light. The photocurrents of the samples were compared using the solar simulator and an Argon-Ionized laser and normalized for mA/cm2 at 0.2 VAg/AgCl. The open circuit potential plots revealed that in the case of coherent light, the photopotential generation was much higher. The Mott-Schottky plots were used to calculate the charge carrier density, and it was shown that in the presence of coherent light the charge carrier density increased eighteen fold. The potentiodynamic curves showed that there was more room for band bending, which allowed the increase in photocurrent density after the saddle point potentials. The difference in photo activity can also be attributed to the fact that a larger length of the nanotube was photoactive. Considering the experimental results, the coherent light was more efficient in increasing the photoactivity of the nanostructured samples, than sunlight. As this is an experimental comparison, a model can be developed in the future to substantiate these results. |
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