In Situ-Formed PdFe Nanoalloy and Carbon Defects in Cathode for Synergic Reduction–Oxidation of Chlorinated Pollutants in Electro-Fenton Process

• DOI: 10.1021/acs.est.9b05896
• Publication Date: 2020-01-24T18:11:33Z
• Authors: Xuqian Shen; Fan Xiao; Hongying Zhao; Ying Chen; Chao Fang; Rong Xiao; Wenhai Chu; Guohua Zhao
• Keywords: 0211 other engineering and technologies; Hydrogen Peroxide; 02 engineering and technology; 7. Clean energy; Carbon; Electrolysis; Water Purification; 13. Climate action; Environmental Pollutants; Electrodes; Oxidation-Reduction; Water Pollutants, Chemical

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.