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

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.