Integrated carbon nanotube fiber free-standing cathode for efficient metal-free H2O2 electrosynthesis and electro-fenton process

Abstract

Electro-Fenton (EF) process is a promising strategy for sustainable water purification, but its application is hindered by catalyst leaching, iron sludge formation, and the short lifetime of hydroxyl radicals. Herein, an oxidized carbon nanotube fiber (Oxi-CNTF) is harnessed as a freestanding metal-free catalytic cathode for generation of H2O2 and conversion into singlet oxygen (1O2) to decompose organic pollutants. Oxi-CNTF is prepared by thermal oxidation of directly spun CNTFs to introduce oxygen-containing functional groups for 2e− oxygen reduction reaction (ORR). The Oxi-CNTF exhibits 3.5-fold higher H2O2 yields than the spray-coated oxidized carbon nanotube (Oxi-CNT) on a carbon paper. The Oxi-CNTF leads to complete degradation of methylene blue (MB) within 1 h, retained >97 % efficiency over 10 cycles, and demonstrates stable activity across a broad pH range (3–9) and in river, tap, and sea water. Furthermore, Oxi-CNTF is woven into fabrics for scalable EF process with >96 % removal efficiency of MB. Mechanistic studies identify 1O2 as the dominant reactive species, providing longer lifetime, salt tolerance, and non-selective degradation pathways superior to hydroxyl radical. This work establishes Oxi-CNTF as an integrated durable catalytic cathode for ORR and EF process, advancing sustainable solutions for H2O2 production and environmental remediation.