Professor Haiou Song published a research paper in Chemosphere (2019 (226): 329-339)
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 Ti3þ 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 Ti3þ 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 in- termediates 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.