Graphene-based sponges for electrochemical degradation of persistent organic contaminants

TL;DR

This study demonstrates that graphene-based doped sponges effectively degrade persistent organic contaminants through electrochemical processes, with high removal efficiency and low chlorate formation, using a cost-effective production method.

Contribution

The paper introduces a low-cost, versatile method for producing doped graphene sponges capable of efficient electrochemical degradation of contaminants in flow-through systems.

Findings

>90% contaminant removal at 173 A/m²

Low chlorate formation (<0.04%) with NaCl

Selective degradation of aromatic C-I bonds

Abstract

Graphene-based sponges doped with atomic nitrogen and boron were applied for the electrochemical degradation of persistent organic contaminants in one-pass, flow-through mode, and in a low-conductivity supporting electrolyte. The B-doped anode and N-doped cathode was capable of >90% contaminant removal at the geometric anodic current density of 173 A m2. The electrochemical degradation of contaminants was achieved via the direct electron transfer, the anodically formed O3, and by the OH radicals formed by the decomposition of H2O2 produced at the cathode. The identified transformation products of iopromide show that the anodic cleavage of all three C-I bonds at the aromatic ring was preferential over scissions at the alkyl side chains, suggesting a determining role of the pi-pi interactions with the graphene surface. In the presence of 20 mM sodium chloride (NaCl), the current efficiency for chlorine production was <0.04%, and there was no chlorate and perchlorate formation, demonstrating a very low electrocatalytic activity of the graphene-based sponge anode towards chloride. Graphene-based sponges were produced using a low-cost, bottom-up method that allows easy introduction of dopants and functionalization of the reduced graphene oxide coating, and thus tailoring of the material for the removal of specific contaminants.