title: Synthesis and Stabilization of Blue-Black TiO2Nanotube Arrays for Electrochemical Oxidant Generation and Wastewater Treatment.
abstract: Efficient, inexpensive, and stable electrode materials are key components of commercially viable electrochemical wastewater treatment system. In this study, blue-black TiO2nanotube array (BNTA) electrodes are prepared by electrochemical self-doping. The 1-D structure, donor state density, and Fermi energy level position are critical for maintaining the semimetallic functionality of the BNTA. The structural strength of the BNTA is enhanced by surface crack minimization, reinforcement of the BNTA-Ti metal interface, and stabilized by a protective overcoating with nanoparticulate TiO2(Ti/EBNTA). Ti/EBNTA electrodes are employed as both anodes and cathodes with polarity switching at a set frequency. Oxidants are generated at the anode, while the doping levels are regenerated along with byproduct reduction at the cathode. The estimated maximum electrode lifetime is 16 895 h. Ti/EBNTA has comparable hydroxyl radical production activity (6.6 × 10-14M) with boron-doped diamond (BDD, 7.4 × 10-14M) electrodes. The chlorine production rate follows a trend with respective to electrode type of Ti/EBNTA > BDD > IrO2. Ti/EBNTA electrodes operated in a bipolar mode have a minimum energy consumption of 62 kWh/kg COD, reduced foam formation due to less gas bubble production, minimum scale formation, and lower chlorate production levels (6 mM vs 18 mM for BDD) during electrolytic wastewater treatment.
authors.affiliation: Linde + Robinson Laboratories California Institute of Technology 1200 E. California Blvd. MC 131-24 Pasadena, California 91125, United States.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Linde + Robinson Laboratories California Institute of Technology 1200 E. California Blvd. MC 131-24 Pasadena, California 91125, United States.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hoffmann
mesh_terms: D001895:Boron / Q000737:chemistry; D018130:Diamond / Q000737:chemistry; D004563:Electrochemistry; D004566:Electrodes; D043942:Nanotubes; D016877:Oxidants; D010084:Oxidation-Reduction; D062065:Wastewater
chemical_list: D001895:Boron; D018130:Diamond; D016877:Oxidants; D062065:Wastewater