The effect of counter electrodes on the photodegrading performances of azoic dye using TiO₂ nanotubes arrays

The novelty of this work is to fabricate the double-walled (DW) TiO₂ nanotube arrays (TNAs) by an anode oxidation method with NH₄F-based electrolyte and Zinc counter electrode (CE, c-Zn) and to investigate the photodegradation performance of these TNAs. The structural, optical, and photodegradation performance of TNAs with c-Zn material have been compared to the properties of TNAs with the other two CEs like c-Pt (Platinum) and c-Ti (Titanium). The counter electrode has a tremendous influence on the structural properties and geometrical features of TNAs. The TNAs fabricated with c-Zn have the red-shifted absorption edge with two bandgaps such as 3.15 and 1.78 eV. Interestingly, the TNAs with c-Zn are found as the DW TNAs with outer diameter of 130 ± 3 nm, thinner outer wall thickness of 12 ± 2 nm, and thicker inner wall thickness of 30 ± 2 nm. The photodegradation performance varies with different counter electrodes during the deposition of TNAs by the anode oxidation method. The TNAs sample prepared with c-Zn has shown the highest roughness value of 305.0 nm, photodegradation efficiency of 97.0%, and the rate constant value of 0.00985 min⁻¹ than the other TNAs with c-Pt, c-Ti, and other researcher's data. Moreover, the optical, structural, and surface morphological properties of TNAs have correlated with the photodegradation performance of TNAs prepared with various counter electrodes during deposition.