Unveiling dual-pathway H2O2 activation in a MgFe2O4/CNT composite for enhanced electrocatalytic degradation of phenol

Abstract

Spinel-structured materials are considered promising electrocatalysts for environmental remediation, yet their mechanisms in the electrocatalytic reduction of O₂ to H₂O₂ and the activation of H₂O₂ remain poorly understood. Herein, we synthesized a novel MgFe₂O₄/carbon nanotube (CNT) composite via a hydrothermal method and systemically investigated its electrocatalytic performance in the degradation of phenol through the in situ electrocatalytic-reduction of O₂ to H₂O₂ and activation to ˙OH. The composite exhibited exceptional catalytic activity, achieving 99% phenol degradation within 30 minutes under optimized conditions (MgFe₂O₄/CNT mass ratio of 10 : 1, applied voltage of −0.9 V, pH 3, and catalyst loading of 0.44 mg cm⁻²). 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 indicate that introducing CNTs considerably improves electron transfer and enriches active oxygen and defect degrees. Importantly, abundant defects and active oxygen species facilitate the generation of H₂O₂ and dominate the conversion of H₂O₂ into ˙OH by heterogeneous activation for MgFe₂O₄/CNT, while MgFe₂O₄ mainly depends on homogeneous activation. This work offers a significant case for the degradation of organic contaminants utilizing spinel-structured electrocatalysts.