Graphite fiber felt modification at room temperature for enhanced and selective H₂O₂ electro-production

Abstract

Hydrogen peroxide (H₂O₂) is widely used in water treatment, disinfection, and chemical synthesis. A sustainable and on-site method for H₂O₂ production is electrochemical synthesis via the two-electron oxygen reduction reaction. This study investigated the enhancement of H₂O₂ electro-production via acidic oxidation of graphite fiber felt (GF) at room temperature using sulfuric acid (H₂SO₄), nitric acid (HNO₃), and hydrochloric acid (HCl). Characterization using scanning electron microscopy, Raman spectroscopy, Fourier-transform infrared spectroscopy, conductivity measurements, and contact angle analysis revealed significant structural and surface changes post-treatments, introducing structural defects, enriched functional groups, enhanced hydrophilicity, and reduced conductivity. Electrochemical analyses, including cyclic voltammetry and rotating ring disk electrode techniques, confirmed improved H₂O₂ selectivity and yield, with optimal electro-production observed for 4 M H₂SO₄, 7 M HCl, and 10 M HNO₃ treatments. H₂SO₄-treated GF exhibited the highest activity, achieving equilibrium H₂O₂ concentrations of 163.9 mg/L, exceeding raw (8.5 mg/L), HCl-treated (41.0 mg/L) and HNO₃-treated (46.4 mg/L) GFs. Pearson correlation analysis revealed strong linear relationships between the GF properties (i.e., defects, conductivity, functional groups, and hydrophilicity) and H₂O₂ electro-production. Electrochemical activity and selectivity correlated strongly with these modified properties, validating their collective role in enhancing electro-production efficiency.