Dechlorination of Trichloroacetic Acid Using a Noble Metal-Free Graphene–Cu Foam Electrode via Direct Cathodic Reduction and Atomic H*

Abstract

A three-dimensional graphene−copper (3D GR−Cu) foam electrode prepared by chemical vapor deposition method exhibited superior electrocatalytic activity toward the dechlorination of trichloroacetic acid (TCAA) as compared to the Cu foam electrode. The cyclic voltammetry and electrochemical impedance spectra analysis confirmed that GR accelerated the electron transfer from the cathode surface to TCAA. With the applied cathode potential of −1.2 V (vs SCE), 95.3% of TCAA (500 μg/L) was removed within 20 min at pH 6.8. TCAA dechlorination at the Cu foam electrode was enhanced at acidic pH, while a slight pH effect was observed at the GR−Cu foam electrode with a significant inhibition for Cu leaching. The electrocatalytic dechlorination of TCAA was accomplished via a combined stepwise and concerted pathway on both electrodes, whereas the concerted pathway was efficiently promoted on the GR−Cu foam electrode. The direct reduction by electrons was responsible for TCAA dechlorination at Cu foam electrode, while at GR−Cu foam electrode, the surface-adsorbed atomic H* also contributed to TCAA dechlorination owing to the chemical storage of hydrogen in the GR structure. Finally, the potential applicability of GR−Cu foam was revealed by its stability in the electrocatalytic dechlorination over 25 cycles.

Reductive dechlorination of trichloroacetic acid (TCAA) by electrochemical process over Pd-In/Al2O3 catalyst

“…Alternatively, the electrochemical treatment of TCAA was found to be more promising as it ensures the selective removal of chlorine atoms from TCAA, while no toxic byproducts are produced [11][12][13][14]. Two main steps, namely, direct dechlorination by electron transfer and an indirect process induced by atomic H*, take place during the electrocatalytic reduction process [15]. Generally, in contrast to the low reduction efficiency of electron transfer, the catalytically produced atomic H* plays a predominant role in dechlorination.…”

Graphene-modified nickel foam electrode for cathodic degradation of nitrofuranzone: Kinetics, transformation products and toxicity

“…In addition, NFZ degradation was promoted by decreasing pH from 8.60 to 4.28 (Figure 3c). The generation of atomic H* is favored in acid solutions, therefore acidic solution facilitates the reduction process by consuming H* [41][42][43]. Even so, NFZ degradation efficiency reached up to 83 % at pH 8.60 within 30 min, suggesting that the GR-Ni foam electrode could be used in a wide range of pH for NFZ degradation.…”

“…More negative cathode potential could produce more available electrons leading to higher efficiency in NFZ reduction. NFZ was nearly completely degraded at the applied potential of It has already been reported that dissolved oxygen could compete with the contaminant for both the electrons and atomic H* on the cathode surface, suppressing thus the target contaminant reduction [27,41]. By purging the solution with N2, the dissolved oxygen was removed.…”

“…It is believed that electrocatalytic reduction of organic pollutants involves direct electron transfer reduction and atomic H*-mediated reduction [41][42][43]. Tertiary butanol (t-BuOH) as a scavenger of H* [44] was used to study NFZ degradation.…”

Graphene: An Outstanding Multifunctional Coating for Conventional Materials

“…f) Electrocatalytic dechlorination of TCAA at the Cu foam and graphene@Cu foam electrodes. Reproduced with permission . Copyright 2016, American Chemical Society.…”