Highly efficient electro-generation of H2O2 by a nitrogen porous carbon modified carbonaceous cathode during the oxygen reduction reaction

Abstract

In this work, active carbon fibers (ACFs) were modified with nitrogen-doped porous carbon (NPC) and carbon nanotubes (CNTs) to prepare a novel modified electrode as a cathode. The effect of different CNT mass ratios on NPC-modified ACFs in H₂O₂ production and electric energy consumption (EEC) were investigated and the optimal CNT mass ratio was found to be 1 : 7. It was observed that H₂O₂ production with NPC-CNTs/ACFs as a cathode (1554.55 mg L⁻¹) was much greater than with raw ACFs as a cathode (59.96 mg L⁻¹). The detection results from scanning electron microscopy, X-ray photoelectron spectroscopy, linear sweep voltammetry and Raman spectroscopy showed a higher electrochemical performance and abundant pyridinic N and oxygen containing functional groups on the cathode after modification, which exposes more defects and oxygen active sites to speed up the oxygen reduction reaction (ORR) and improve the electrocatalytic activity of the electrode. H₂O₂ production could also achieve a balance with a high yield of H₂O₂ production (around 1550 mg L⁻¹) with low EEC (<30.08 kW h kg⁻¹) in six consecutive runs. Moreover, The total organic carbon (TOC) removal rate of pharmaceuticals and personal care products (PPCPs:, tetracycline hydrochloride and diclofenac sodium) via an electro-Fenton (EF) process on the modified cathode was over 100% in 50 min, while the TOC removal of tetracycline hydrochloride and diclofenac sodium reached 69.5% and 79.2%, respectively, after 2 h, which was more than four and five times that on the unmodified catalyst (9.60% and 16.27%). Such a loaded cathode gave high efficiency and a significant increase in H₂O₂ generation, and degraded organic pollutants via an EF process with high efficiency and low energy consumption.