Kinetics and mechanisms of electrocatalytic hydrodechlorination of diclofenac on Pd-Ni/PPy-rGO/Ni electrodes

Abstract

In order to improve the dispersibility of the catalytic metal in the palladium-based catalyst and reduce the cost of the palladium electrode, a low palladium loading Pd-Ni bimetallic electrode (PdNi/PPy-rGO/Ni foam) was synthesized by an electrodeposition method. The deposition current for metal loading was 7 mA, the temperature was 40 ℃, and the molar ratio of bimetallic palladium-nickel was 5:1. The PdNi/PPy-rGO/Ni foam electrode exhibited high electrocatalytic performance for diclofenac degradation with a dechlorination efficiency of 100 % in 140 min. Besides, the catalytic metal particles in the bimetallic PdNi/PPy-rGO/Ni foam electrode had better dispersion and smaller catalytic metal particle size, with an average particle size of 3.3 nm, smaller than that of the single metal Pd/PPy-rGO/Ni electrode of 5 nm. Besides, the doping of rGO and nickel accelerated the electrochemical reaction kinetics on the surface of PdNi/PPy-rGO/Ni electrode and promoted the generation of hydrogen atom (H*). Furthermore, the PdNi/PPy-rGO/Ni foam exhibited better resistance to sulfite. The dechlorination mechanism and degradation pathway of diclofenac by PdNi/PPy-rGO/Ni electrode were proposed. Overall, the PdNi/PPy-rGO/Ni foam electrode exhibited good performance and stability. Hence, the PdNi/PPy-rGO/Ni foam electrode possesses good potential for the treatment of aquatic environments with chlorinated pollutants.