Self-doped TiO2 nanotube arrays for electrochemical mineralization of phenols. (July 2019)

• Record Type: Journal Article
• Authors: Gan, Ling; Wu, Yifan; Song, Haiou; Lu, Chang; Zhang, Shupeng; Li, Aimin
• Is Part Of: Chemosphere. Volume 226(2019)
• Page Start: 329
• Page End: 339
• Publication Date: 2019-07
• Subjects: Ti3+ -- TiO2 nanotubes -- Anode material -- Electrochemical oxidation -- Mineralization; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.03.135
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Self-doped TiO2 nanotube arrays (DNTA) were prepared for the electrooxidation of resistant organics. The anatase TiO2 NTAs had an improved carrier density and conductivity from Ti 3+ doping, and the oxygen-evolution potential remained at a high value of 2.48 V versus the standard hydrogen electrode, and thus, achieved a highly enhanced removal efficiency of phenol. The second anodization could stabilize Ti 3+ and improve the performance by removing surface TiO2 particles. Improper preparation parameters (i.e., a short anodization time, a high calcination temperature and cathodization current density) harmed the electrooxidation activity. Although boron-doped diamond (BDD) anodes performed best in removing phenol, DNTA exhibited a higher mineralization of phenol than Pt/Ti and BDD at 120 min because intermediates were oxidized once they are produced with DNTA. Mechanism investigations using reagents such as tert-butanol, oxalic acid, terephthalic acid, and coumarin showed that the DNTA mineralization resulted mainly from surface-bound OH, and the DNTA produced more than twice the amount of OH compared with BDD. The free OH on the BDD electrode was more conducive to initial substrate oxidation, whereas the adsorbed OH on the DNTA electrode mineralized the organics in situ. The preferential removal of p -substituted phenols on DNTA was attributed mainly to their electromigration and the aromatic intermediates that are hydrophobic were beneficial to mineralization. Graphical abstract: Image 1 Highlights: The DNTA showed excellent oxidation efficiency by dopping appropriate Ti 3+ . DNTA exhibited lower removal but higher mineralization efficiency for phenol than BDD. Surface-bound .OH was a dominant mechanism for the mineralization. The electrooxidation efficiencies of different p-substituted phenols were investigated.