Cost-effective degradation of pollutants by in-situ electrocatalytic process on Fe@BN-C bifunctional cathode: Formation of 1O2 with high selectivity under nanoconfinement

Electrochemical advanced oxidation processes (EAOPs) capable of in-situ producing highly active species are regarded as promising technologies for organic pollutants removal without chemicals addition, however their efficiency is not cost-effective especially under neutral and alkaline condition. Herein, an in-situ electrocatalytic process using bifunctional cathode of N, B-codoped carbon nanotubes with embedded nano-iron particles (Fe@BN-C) was developed, which simultaneously achieved the efficient generation of H2O2 and selective formation of 1O2. The Fe@BN-C cathode exhibited higher activity for sulfamethazine (SMT) degradation (5.6-folds faster) and H2O2 generation (3.6-folds higher) than OH-mediated non-confined analog. Also it exhibited promising application prospect for treatment of various pollutants and real wastewaters over wide pH ranges to 9 with the electrical energy consumption (EEC, 0.064 kWh log−1 m−3 for SMT degradation) only one tenth of the conventional electro-Fenton. Density functional theory calculations and in-situ Fourier transformed infrared spectroscopy verified that the presence of hexagonal boron nitride (h-BN) enhanced the H2O2 selectivity (close to 100 %), and H2O2 as intermediate in the presence of Fe0 could be electrochemically converted into OOH/O2− and further activated by the generated surface OH to form 1O2. This work will provide new insight into the design and understanding of efficient in-situ electrocatalytic process by bifunctional cathode with nanoconfinement for water purification.