Synergistically S/N self-doped biochar as a green bifunctional cathode catalyst in electrochemical degradation of organic pollutant

Abstract

Biomass-derived heteroatom self-doped cathode catalysts has attracted considerable interest for electrochemical advanced oxidation processes (EAOPs) due to its high performance and sustainable synthesis. Herein, we illustrated the morphological fates of waste leaf-derived graphitic carbon (WLGC) produced from waste ginkgo leaves via pyrolysis temperature regulation and used as bifunctional cathode catalyst for simultaneous H2O2 electrochemical generation and organic pollutant degradation, discovering S/N-self-doping shown to facilitate a synergistic effect on reactive oxygen species (ROS) generation. Under the optimum temperature of 800 °C, the WLGC exhibited a H2O2 selectivity of 94.2% and tetracycline removal of 99.3% within 60 min. Density functional theory calculations and in-situ Fourier transformed infrared spectroscopy verified that graphitic N was the critical site for H2O2 generation. While pyridinic N and thiophene S were the main active sites responsible for ˙OH generation, N vacancies were the active sites to produce 1O2 from O2. The performance of the novel cathode for tetracycline degradation remains well under a wide pH range (3–11), maintaining excellent stability in 10 cycles. It is also industrially applicable, achieving satisfactory performance treating in real water matrices. This system facilitates both radical and non-radical degradation, offering valuable advances in the preparation of cost-effective and sustainable electrocatalysts and hold strong potentials in metal-free EAOPs for organic pollutant degradation.

Keywords

• Biochar
• S and N self-doping
• H2O2 production
• In-situ FTIR
• Metal-free electrochemical advanced oxidation processes