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

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 consecutive reaction with a carbon defect and PdFe. Complete total organic carbon (TOC) removal and dechlorination of 3-chlorophenol was achieved 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 2 h due to 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.