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

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 selfenhanced 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.

Accelerated Fe2+ Regeneration in an Effective Electro-Fenton Process by Boosting Internal Electron Transfer to a Nitrogen-Conjugated Fe(III) Complex

“…Electro-Fenton (EF) represents an important eco-friendly version of advanced oxidation processes (AOPs), since the risk in the transportation and operation of H 2 O 2 in the conventional Fenton process could be avoided. − In the EF process, a two-electron oxygen reduction reaction (ORR) occurs at the cathode to generate H 2 O 2 , which could subsequently react with ferrous ions (Fe 2+ ) to produce hydroxyl radicals (·OH) . The high redox potential of ·OH (1.8–2.7 V) renders strong oxidation ability to the degradation of various organic recalcitrant pollutants including dyestuffs, pharmaceuticals, and pesticides from food, tanning, and petrochemical industries. − However, the EF process suffers from low utilization efficiency of H 2 O 2 for the generation of ·OH as well as undesirable precipitation of iron oxy-hydroxides, because of the rapid accumulation of Fe 3+ via eq but slow regeneration of Fe 2+ via eq . − …”

Interface-modulated nanojunction and microfluidic platform for photoelectrocatalytic chemicals upgrading

“…Although promising PEC performances have been achieved, the charge transfer mechanisms remain unclear and are still under debate in many cases [28,29]. On the other hand, the mass transfer of reactants and their subsequent adsorption on the electrode surface are also essential factors determining the reaction rate and efficiency [30,31]. However, most current prevailing approaches for PEC oxidative upgrading focus on planar photoelectrodes, which suffer from low efficiency caused by limited reactants diffusion around the semiconductor-liquid interface [32][33][34][35].…”

Engineering Noble Metal Nanomaterials for Pollutant Decomposition

“…In addition, Pt nanoparticles can activate the surface oxygen species of TiO 2 and become negatively charged, and then, the negatively charged Pt nanoparticles are the active sites for formaldehyde oxidation. Correspondingly, the researchers found that metallic (Pt 0 ) or negatively charged Pt species showed higher oxidation catalytic activity than PtO or Pt 4+ , and H 2 reduction treatment for the supported Pt nanoparticles can improve the catalytic activity at ambient temperature (Figure a–c). − On the other hand, several recent studies have investigated the effect of Pt nanoparticles parameters on catalytic performance, such as particle size and dispersion. As the particle size increases, the Pt atoms on the crystal phase increase and provide more active sites for catalytic oxidation .…”

“…This system can degrade RhB within 30 min, and the excess H + generated at the anode can provide a suitable pH environment for the reaction between H 2 O 2 and Fe 2+ to generate HO• (Figure b, c) . In addition, a number of studies found that Pd nanoparticles directly deposited on iron oxides can also simultaneously generate H 2 O 2 and Fe 2+ . ,− For example, Luo et al developed an electron Fenton system based on Pd/Fe 3 O 4 nanoparticles. The system can remove 98% of phenol (20 mg/L) within 60 min without adding any other chemicals.…”