Unveiling Dual-Pathway H2O2 Activation in MgFe₂O₄/CNT Composite for Enhanced Electrocatalytic Degradation of Phenol

Abstract

Spinel-structured materials are considered as promising electrocatalysts for environmental remediation, yet their mechanisms in electrocatalytic reduction of O2 to H2O2 and activation of H2O2 remain poorly understood. Herein, we synthesized novel a MgFe2O4/carbon nanotube (CNT) composite via a hydrothermal method and systemically investigated its electrocatalytic performance in the degradation of phenol through in-situ electrocatalytic-reduction O2 to H2O2 and activation to ·OH. The composite exhibited exceptional catalytic activity, achieving 99% phenol degradation within 30 minutes at optimized conditions (MgFe2O4/CNT ratio of 0.6:1, applied voltage of -0.9 V, pH 3, and catalyst loading of 0.44 mg/cm2). Moreover, the total organic carbon (TOC) reached 78.6% in 90 minutes, with the catalyst maintaining 91.4% efficiency after four recycling experiments. Mechanistic studies using XPS and control experiments indicates CNTs introduction considerably improve the electron transfer and enrich active oxygen and defect degree. Importantly, abundant defects and active oxygen species facilitates the generation of H2O2 and dominates conversion of H2O2 into ·OH by heterogeneous activation for MgFe2O4/CNT, while MgFe2O4 mainly depends on the homogeneous activation. This work offers a significative case for the degradation of organic contaminants utilizing spinel-structured electrocatalysts.