title: WITHDRAWN: A three-step electrochemical method designed for the production of nickel- and platinum-doped TiO(2) multi-nanoporous thin-film electrodes: An application in the degradation of acid red G.
abstract: This study reports on the production of the platinum- and nickel-doped anatase multi-nanoporous thin-film electrodes. These doped electrodes were fabricated from titanium plates by a three-step electrochemical method, which comprises (i) anodization of titanium plates in oxalic acid electrolyte, (ii) electrodeposition of transition metals on the oxide produced, and finally, (iii) re-anodization of the whole assembly in sulfuric acid electrolyte, which leads to the production of stable transition metal-doped TiO(2) thin-film electrodes. Some investigations concerning the degradation of a non-biodegradable azo dye (acid red G) in the presence of these electrodes irradiated by artificial UV-light were performed. The degradation of about 92% was obtained at pH 2.1 after 5.0h illumination of acid red G 23ppm using TiO(2) electrode while only about 50% degradation was observed at pH 12.2. The photocatalytic degradation of the dye was strongly favored in acidic solutions. A simplified kinetic study of the degradation of the dye by UV/TiO(2) electrodes system was carried out and the adsorption equilibrium constant (K(ads)), the pseudo-first order rate constant (k), and the degradation rate (r) were evaluated for different electrodes. The ratios of the degradation rates of acid red G 23ppm in respect with the undoped TiO(2) were 2.63, 1.00, and 0.58 using Pt-TiO(2), TiO(2), and Ni-TiO(2), respectively. The photocatalytic efficiency was remarkably enhanced in samples doped with Pt(4+) while the incorporation of Ni(2+) was detrimental to this process. The efficiency of the metal-doped TiO(2) electrodes was explained on the basis of the electroaffinity and the electron work function. The COD removal of about 86.3% was obtained at pH 2.1 after 3.0h illumination of acid red G 7.5ppm using Pt-TiO(2) electrode. The experimental results showed that the reduction of COD removal decreased with increasing pH and the augmentation of the initial concentration of the azo dye.
authors.affiliation: Institute of Materials, Shanghai University, 149 Yanchang Road, Shanghai 200072, People's Republic of China.
authors.forename: Ekoko Bakambo
authors.initials: EB
authors.lastname: Gracien
authors.forename: Jianian
authors.initials: J
authors.lastname: Shen
authors.forename: Xianrong
authors.initials: X
authors.lastname: Sun
authors.forename: Dong
authors.initials: D
authors.lastname: Liu
authors.forename: Moucheng
authors.initials: M
authors.lastname: Li