Fabrication of a self-doped TiO2 nanotube array electrode for electrochemical degradation of methyl orange

Self-doped TiO 2 nanotube array (DTNA) electrodes were fabricated through anodic oxidation combined with cathodic reduction. The morphology and structural features of pristine TiO 2 nanotube arrays and DTNA electrodes were studied through scanning electron microscopy, X-ray diffractometry, and X-ray photoelectron spectroscopy. An accelerated life test was used to test the electrode service lifetime and thus the electrode's stability. The service lifetime of the DTNA electrode prepared at constant 40 V for 6 hr was approximately 338.7 hr at constant 1 mA/cm 2 in a 1 M NaClO 4 solution. Methyl orange (MO) was employed as the degradation probe for measuring electrochemical oxidation performance. The color removal rate of 200 mg/L MO of the DTNA electrode (85.2% at 1 mA/cm 2 ) was greater than that of the Ti/IrO 2 electrode (31.1% at 1 mA/cm 2 ). The larger the surface area of the DTNA electrode is, the more conductive the electrode is for the degradation of organic substances. Organic degradation on the DTNA electrode occurred primarily through an indirect pathway (producing [∙OH]).