Highly efficient electro-generation of hydrogen peroxide using NCNT/NF/CNT air diffusion electrode for electro-Fenton degradation of p-nitrophenol

To promote the in situ generation of hydrogen peroxide (H₂O₂) in electro-Fenton system, a new air diffusion electrode (ADE) was put forward in the present work using N-doped multi-walled carbon nanotubes (NCNT) as the catalyst layer, multi-walled carbon nanotubes (CNT) as the diffusion layer, and nickel foam (NF) as the supporting material, respectively. The catalyst layer in ADE was characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. Then the performances of H₂O₂ accumulation and p-nitrophenol (p-NP) degradation with the electrode (NCNT/NF/CNT ADE) were investigated. The experimental results showed that H₂O₂ accumulation on the NCNT/NF/CNT ADE was greatly improved by the presence of N doping, and H₂O₂ accumulation concentration could reach 307 mg L⁻¹ after 120 min at the current intensity of 100 mA. Moreover, the NCNT/NF/CNT ADE presented more effective performance on p-NP degradation than the CNT/NF/CNT ADE or the NF ADE. p-NP of initial 50 mg L⁻¹ could be almost completely removed after 30 min, and the total organic carbon removal efficiency reached 62.61% after 120 min when 0.4 mM Fe²⁺ was added into the system. The repeatability test suggested that the stability of the NCNT/NF/CNT ADE was very good.