Electrocatalytic degradation of 2,4-dichlorophenol by a 3DG-PbO2 powdered anode: Experimental and theoretical insights

Abstract A novel nano powdered PbO2 (NP-PbO2) 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-PbO2 to solve this problem. Due to the multidimensional electrical transmission channels provided by 3DG, the charge transfer resistance of NP-PbO2 was greatly reduced from 3.08 × 105 to 7.74 × 103 Ω/cm2, thereby significantly boosting the hydroxyl radical generation capacity of NP-PbO2 electrode. In electrocatalytic oxidation process of 2,4-dichlorophenol (2,4-DCP), the optimal 3DG-PbO2 composite anode exhibited excellent eletrocatalytic activity. After 60 min of electrolysis, the mineralization current efficiency at 3DG-PbO2 electrode was 1.68 and 3.38 times higher than those at NP-PbO2 and electrodeposited PbO2 (ED-PbO2) 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/cm2, initial 2,4-DCP concentration 50 mg/L, pH 3 and Na2SO4 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-PbO2 anode.