Enhanced Adsorption and Photocatalytic Activity of Vertically Oriented TiO₂ Nanotube Arrays by Li Incorporation

A highly efficient, solid, and easily maneuverable adsorbent and photocatalyst, Li‐incorporated titanate nanotubes that manifest adsorption efficiency of 98.1% and photocatalytic efficiency of 99.6% in 60 min and 97.8% and 98.5%, respectively, in a shorter duration of 20 min, is synthesized by a facile two‐stage electrochemical technique. The modified nanotubes exhibit good cyclic stability of 93.7% photodegradation of malachite green dye after three continuous cycles. The adsorption data show the highest correlation for second‐order pseudo kinetics and Freundlich isotherm, suggesting multilayer chemisorption with an adsorption capacity of k F ≈ 219.51 mg 1–1/ n L 1/ n g −1 . Fourier transform infrared spectroscopy (FTIR) analysis of the adsorbent before and after the adsorption corroborates the findings. X‐Ray photoelectron spectroscopy reveals the formation of a larger number of oxygen vacancies (Ti 3+ /Ti 2+ ) that facilitate more carrier release for the production of reactive oxygen species during photocatalysis. X‐Ray diffraction and transmission electron microscopy analysis confirm a secondary rutile phase formation on Li doping that promotes heterogeneous multilayer adsorption. Field‐emission spectroscopic studies reveal a change in the morphology of the doped tubes with porous aggregate formation on the surface. The structural, morphological, and compositional change brought about by Li incorporation facilitates the use of titania nanotubes as an efficient adsorbent cum photocatalyst in the removal of malachite green dye.