<p>Measures to save our water bodies from pollutants are crucial for the healthy sustenance of life in this age of water scarcity. Photocatalysis is an effective tool for the treatment of water polluted by various industrial effluents. Here, potassium (K) doping is done to engineer the structural, morphological and optical properties of TiO₂ nanotube arrays for the improvement of its photocatalytic degradation efficiency. Doping enhanced the photocatalytic degradation rates to ~ 96% in 120 min and ~ 97% in 180 min, respectively, for crystal violet and methylene blue dyes from the respective values of 70% and 55% for pristine TiO₂ nanotubes. The fabrication and doping of the nanotube arrays vertically aligned over titanium foil are done by the cost-effective electrochemical method. From multiple characterizations, the enhancement in the photocatalytic efficiency of the doped nanotube arrays is ascribed mainly to the drastic reduction in the band gap from UV to the visible range, formation of carrier trap centers by reduction of Ti⁴⁺ to Ti³⁺/Ti²⁺ states, presence of more hydroxyl groups, an increased orientation of K⁺&#xa0;doped nano-crystallites along (004) plane.</p>