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