Abstract
• 3DG and powdered PbO 2 composite anode was fabricated for electrochemical oxidation. • Experimental and theoretical methods were combined to study OH attack to 2,4-DCP. • DFT calculations were performed for HO -addition on benzene of 2,4-DCP. • Degradation pathway of 2,4-DCP was elucidated on the molecular level. A novel nano powdered PbO 2 (NP-PbO 2 ) electrode was fabricated in our previous study as a highly efficient anode material for electrocatalytic oxidation, but it is still challenged by its high charge transfer resistance. Herein, three-dimensional graphene (3DG) was composited with NP-PbO 2 to solve this problem. Due to the multidimensional electrical transmission channels provided by 3DG, the charge transfer resistance of NP-PbO 2 was greatly reduced from 3.08 × 10 5 to 7.74 × 10 3 Ω/cm 2 , thereby significantly boosting the hydroxyl radical generation capacity of NP-PbO 2 electrode. In electrocatalytic oxidation process of 2,4-dichlorophenol (2,4-DCP), the optimal 3DG-PbO 2 composite anode exhibited excellent eletrocatalytic activity. After 60 min of electrolysis, the mineralization current efficiency at 3DG-PbO 2 electrode was 1.68 and 3.38 times higher than those at NP-PbO 2 and electrodeposited PbO 2 (ED-PbO 2 ) electrodes, respectively. The influence of several important operation parameters on the 2,4-DCP removal efficiency was examined. The results show that the 2,4-DCP removal reached 97.67% after 80 min of electrolysis under the conditions of current density 4 mA/cm 2 , initial 2,4-DCP concentration 50 mg/L, pH 3 and Na 2 SO 4 concentration 0.05 M. In addition, the degradation mechanism of 2,4-DCP was explored via theoretical computation (frontier molecular orbitals, molecular electrostatic potential, total charges, Fukui functions and transient states) and experimental identification of intermediates. Accordingly, we proposed the mineralization pathway of 2,4-DCP at the 3DG-PbO 2 anode.
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