Cu2O nanoparticles anchored on 3D bifunctional CNTs/copper foam cathode for electrocatalytic degradation of sulfamethoxazole over a broad pH range.

In this paper, nanoscale Cu2O particles was successfully anchored at defect sites of carbon nanotubes (CNTs), which doped on three-dimensional copper foam (CF) electrode (Cu2O@CNTs/CF). The compound as cathode was synthesized via dip-coating and rapid electrodeposition followed by annealing procedure, and conducted in heterogeneous electro-Fenton (EF) system. The Cu2O@CNTs/CF composites electrode enabled activate O2 to generate H2O2 in situ and further Cu0/Cu2O synergistic catalysis to produce reactive oxygen species for a broad pH-range via the heterogeneous EF process. Cu0 on the surface of CF also contributed to the reduction of Cu2+ to Cu+, thereby enhancing the stability of the electrode. The effects of critical parameters such as precursor-ligand dosage, the initial pH value, initial pollutant concentration and current density on the degradation of the antibiotic sulfamethoxazole (SMX) were investigated. The as-obtained electrode performed both effective catalytic activity and good reusability. Almost 100% removal rate was reached within 75 min over a broad pH range (3 to 11) during the heterogeneous EF process, with the current density of 12 mA cm-2 and the removal efficiency of SMX decreased by only 9.0% after 8 recycle runs. Furthermore, quenching experiments indicated that hydroxyl radicals (·OH) were main species responsible for the SMX oxidation. In addition, the possible degradation pathways of SMX were proposed, which were based on nine identified intermediates. The comprehensive work is elucidated to accelerate the development of the in-situ production of H2O2 during the heterogeneous EF system and provide new insights to achieve high-efficiency degradation of pollutants via copper-based catalytic materials.