Enhanced degradation of refractory organics in ORR-EO system with a blue TiO2 nanotube array modified Ti-based Ni-Sb co-doped SnO2 anode

ABSTRACT Recently, a novel 2-electron oxygen reduction reaction (ORR) based electro-oxidation (EO) system was developed, which utilizes a H 2 O 2 generation cathode instead of H 2 evolution cathode. A Ti-based Ni-Sb co-doped SnO 2 (Ti/NATO) anode was selected for efficient degradation of refractory organics and O 3 production. The synergistic reaction of O 3 /H 2 O 2 further accelerated the generation of hydroxyl radicals ( • OH) in the ORR-EO system. However, the catalytic activity and long-term effectiveness of the Ti/NATO anode limited the large-scale application of the ORR-EO process. In this study, a blue TiO 2 nanotube array (blue-TiO 2 -NTA) inter-layer was introduced into the fabrication process between the Ti substrate and NATO catalyst layer. Compared to the Ti/NATO anode, the Ti/blue-TiO 2 -NTA/NATO anode achieved higher efficiency of organic removal and O 3 generation. Additionally, the accelerated lifetime of the Ti/blue-TiO 2 -NTA/NATO anode was increased by 7 times compared to the Ti/NATO anode. When combined with CNTs-C/PTFE air cathode in ORR-EO system, all anodic oxidation and O 3 /H 2 O 2 processes achieved higher • OH production. Over 92% of TOC in leachate bio-effluent was effectively eliminated with a relatively low energy cost of 45 kWh/t.