In Situ-Formed PdFe Nanoalloy and Carbon Defects in Cathode for Synergic Reduction–Oxidation of Chlorinated Pollutants in Electro-Fenton Process
Xuqian Shen, Fan Xiao, Hongying Zhao, Ying Chen, Chao Fang, Rong Xiao, Wenhai Chu, Guohua Zhao
Abstract
Complete dechlorination and mineralization of chlorophenols via the reduction–oxidation-mediated electro-Fenton process with a composite bulk cathode is first proposed. The in situ formation of a PdFe nanoalloy and carbon defects as key active sites is mutually induced during the formation of a carbon aerogel-based electrode. Specifically, the PdFe nanoalloy promotes the generation of [H]ads as reduction sites and improves the electron transfer via an electrical circuit, while the carbon defects selectively favor the 2e– oxygen reduction pathway. Notably, this work implies a novel electrocatalytic model for the formation of ·OH via (2 + 1)e– oxygen reduction by a consecutive reaction with carbon defects and a PdFe nanoalloy. Complete total organic carbon removal and dechlorination of 3-chlorophenol were performed after 6 h. The kinetic rate constant for removing haloacetamides (HAMs) in drinking water was 0.21–0.41 h–1, and the degradation efficiency was self-enhanced after electrolysis for 2 h because of the increased concentration of [H+]. The specific energy consumption was ∼0.55 W·h·g–1 at 100% removal of some HAMs, corresponding to a power consumption of 0.6–1.1 kW·h for complete dehalogenation per ton of drinking water in waterworks. Moreover, the PdFe alloy/CA exhibited extreme mechanical and electrochemical stability with limited iron (∼0.07 ppm) and palladium (0.02 ppm) leaching during the actual application.