<p>The aim of this study was to develop a low-cost and highly efficient electrocatalyst with high H₂O₂ yield and rapid Fe²⁺ regeneration for the treatment of refractory organic pollutants. In this work, activated g-C₃N₄-modified carbon nanotubes (<i>n</i>-g-C₃N₄/CNT, <i>n</i> = 0.5, 1, 2, mass ratio) were prepared by CNT surface oxidation followed by calcination to enhance electro-Fenton degradation efficiency. The results showed that among the three cathode compositions, the 0.5-g-C₃N₄/CNT cathode achieved the highest electro-Fenton degradation performance, with complete phenol removal within 10 min and a total organic carbon (TOC) removal of 55% after 60 min. The optimized 0.5-g-C₃N₄/CNT cathode achieved nearly complete phenol degradation within 10 min, with a high apparent rate constant of 0.39 min⁻¹, while simultaneously delivering a considerable H₂O₂ generation rate of 85.68 mg L⁻¹ h⁻¹.The enhanced electro-Fenton performance of the g-C₃N₄-modified carbon nanotubes is attributed to promoted electro-generation of H₂O₂ and, at low g-C₃N₄ loading (0.5-g-C₃N₄/CNT), accelerated regeneration of Fe²⁺ from Fe³⁺, thereby facilitating the reaction between Fe²⁺ and in situ generated H₂O₂ to produce highly reactive hydroxyl radicals (·OH). In addition, the electrode exhibited broad applicability to different pollutants and good stability, as demonstrated by degradation experiments and five successive cyclic tests. The superior electro-Fenton performance is attributed to the synergistic coupling of the conductive CNT framework and nitrogen-rich g-C₃N₄, which not only promotes the two-electron oxygen reduction pathway for efficient H₂O₂ production but also accelerates Fe³⁺/Fe²⁺ regeneration, enabling a low-cost and highly efficient electrocatalytic system.</p>