Enhancement of H2O2 production and AYR degradation using a synergetic effect of photo-electrocatalysis for carbon nanotube/g-C3N4 electrodes

Abstract

In this work, a new gas diffusion electrode (GDE) of carbon nanotube/graphitic carbon nitride (CNT/g-C₃N₄) was prepared, which enables the substantially improved production of H₂O₂ (up to 1083.54 mg L⁻¹) compared to generation without g-C₃N₄ (400 mg L⁻¹). Characterized by TEM, XRD and XPS, the synthesized g-C₃N₄ was proved to be a thin layer sheet with low defects. Important cathode manufacturing parameters including the mass ratio of CNTs to g-C₃N₄ were optimized, and the dependence of H₂O₂ generation on pH, current density, aeration rate and performance stability were investigated. Further explored by linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) analysis, the presence of g-C₃N₄ was found to accelerate the electron transfer rate, benefit the oxygen surface reaction, which contributed to the enhanced performance for H₂O₂ production. Finally, such a CNT/g-C₃N₄ cathode demonstrated effectiveness for the degradation of alizarin yellow R (AYR) by electro-Fenton (EF), photo-Fenton (PF) and photoelectron-Fenton (PEF) processes. AYR was degraded completely, and 94.8% of the organic carbon was removed, which is more than 5 times the amount removed using PF degradation only. And during the PEF degradation process of AYR, electro- and photocatalysis support and optimize each other, which produces a substantial synergistic effect, proving great potential for practical application in organic wastewater treatment.