Structure–Activity Relationships of TiO2 nanoflower-coated Porous Ti Anodes in Electro-catazone process

Electrochemical heterogeneous catalytic ozonation (E-catazone) process is a new advanced oxidation process for the efficient degradation of ozone-resistant pharmaceutical micropollutants (PMPs). The TiO2 nanoflower-coated porous Ti gas diffuser (TiO2-NF@PTGD) anode is crucial to the enhanced PMP degradation, ozone decomposition, and ·OH production in the E-catazone process. However, the relationships and mechanisms between the TiO2-NF@PTGD surface properties and the decontamination ability of E-catazone remain unresolved. Thus, through modulating the TiO2-NF surface properties by varying the hydrothermal preparation conditions of TiO2-NF@PTGD anodes, this study investigated the structure–activity relationships between the anodes and the destruction of the ozone-resistant PMP para-chlorobenzoic acid (p-CBA) by E-catazone. The mechanism was further elucidated by material characterization, interfacial kinetics analysis, and reactive oxygen species (ROS) determination. The results showed that the TiO2-NF@PTGD surface properties, including morphology and surface adsorbed oxygen (Oad), were largely influenced by the hydrothermal conditions (time, NaOH concentration, and temperature) and that Oad, presenting surface active sites, showed a significant positive correlation with the p-CBA degradation efficiency, rate, interfacial kinetic properties, ozone decomposition, and ROS production. At the optimized surface properties of Oad proportion of 29.44% and interfacial kinetic constant of 7.00 × 10−5 M−1 s−1, the complete removal of p-CBA with the highest degradation rate of 6.50 × 10−3 s−1, largest instantaneous ozone demand of 6.56 mg L−1, and largest ·OH exposure of 4.39 × 10−10 M s (5 min) were achieved. This study provides the basic parameters for the scale up preparation of TiO2-NF@PTGD electrodes and E-catazone applications.