Efficient Singlet Oxygen Generation via ZIF67@CNT Three-Dimensional Electrodes for Highly Effective Decomposition of Polycyclic Aromatic Hydrocarbon with Low Energy Consumption

Singlet oxygen (O-1(2)) is preferred over free radical in the electrochemical advanced oxidation process (EAOP) due to its selectivity in treating persistent organic pollutants. However, traditional reaction systems still suffer from issues such as low O-1(2) yield and low catalytic efficiency. To address these concerns, this study proposed a new three-dimensional (3D) anode system consisting of carbon nanotube (CNT) with zeolitic imidazolate framework-67 (ZIF-67) in situ loaded as an electrode material. The interplay between the metal species and carbon lattice was utilized to enhance electron transfer, promote the generation of O-1(2), and decompose polycyclic aromatic hydrocarbons (PAHs). The results showed that ZIF67@CNT generated a large amount of O-1(2) at 1.32 V vs standard hydrogen electrode (SHE) to degrade the contaminant. The kinetic rate constants of naphthalene, 1-naphthylamine, 2-naphthol, and 1-nitronaphthalene were calculated to be 0.0971, 0.439, 0.132, and 0.0396 min(-1), respectively. Notably, the kinetic rate constant of 1-naphthylamine was 8-25 times higher than those of other electrochemical technologies. Moreover, the energy cost of 0.39 kWh m(-3) was 1-2 orders of magnitude lower. The combination of electron paramagnetic resonance (EPR) analysis with free radical quenching revealed that O-1(2) played a dominant role in the decomposition process of 1-naphthylamine, although (OH)-O-center dot was also involved.