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The nitrogen/oxygen self-doped porous biochar (NO/PBC) and NO/PBC supported CuFeO 2 (CuFeO 2 -NO/PBC) were prepared and mixed as cathode catalysts for gas diffusion electrode (GDE) fabrication. The fabricated GDE could realize H 2 O 2 electrogeneration and activate H 2 O 2 to produce active radicals through NO/PBC and CuFeO 2 , respectively. The GDE with the NO/PBC to CuFeO 2 -NO/PBC ratio of 1:1 (CuFeO 2 -NO/PBC-GDE-1.0) possessed more superior catalytic performance for tetracycline degradation in heterogeneous photo-electro-Fenton (hetero-PEF) system under visible light than other as-fabricated GDEs. The •OH was primary species, and •O 2 - was auxiliary species for hetero-PEF degradation of tetracycline through CuFeO 2 -NO/PBC-GDE-1.0. The electron on the cathode surface and photoinduced electron could accelerate Fe3+/ Fe2+ and Cu2+/ Cu+ redox cycle, promoting •OH/•O 2 - production and tetracycline degradation. The toxicity estimation of tetracycline and intermediates, TOC removal and Escherichia coli growth inhibition confirmed that the remission of overall toxicity, the inhibition of antibacterial property and the mineralization of tetracycline were achieved in hetero-PEF system. [Display omitted] • CuFeO 2 -NO/PBC was prepared by hydrothermal method using NO/PBC as a support. • CuFeO 2 -NO/PBC-GDE-1.0 was fabricated for the hetero-PEF degradation of tetracycline. • CuFeO 2 -NO/PBC-GDE-1.0 could generate and activate H 2 O 2 to produce active radicals • Cathode electron and photoinduced electron promoted regeneration of Fe2+ and Cu+. • Hetero-PEF system relieved the toxicity and antibacterial property of tetracycline. [ABSTRACT FROM AUTHOR]

[Display omitted] • CuFeO2/NPC composites were prepared at no nitrogen sources and reductant. • CuFeO2/NPC can effectively activate PDS to degrade nimesulide. • The OH, SO4- and 1O2 were the main reactive species for nimesulide degradation. • Mechanism of PDS activated by CuFeO2/NPC was clarified in detail. • Degradation pathway was proposed combined with HPLC/MS spectra and DFT calculation. The nitrogen self-doped porous carbons (NPCs) were prepared using alfalfa as raw material by pyrolysis method without additional nitrogen sources at various pyrolysis temperatures. The NPC supported CuFeO 2 (CuFeO 2 /NPC) composites with large BET surface area (113.18 - 517.56 m2 g−1) were successfully prepared by hydrothermal method without reductant. The NPC prepared at 600 °C (NPC-600) supported CuFeO 2 (CuFeO 2 /NPC-600) possessed the highest catalytic performance for activating peroxydisulfate (PDS) to degrade nimesulide compared to other CuFeO 2 /NPC composites. The OH, SO 4 - and 1O 2 were the main reactive species for nimesulide degradation. The oxygen-containing functional groups, pyridinic N, graphitic N, and Fe3+/Fe2+ and Cu2+/Cu+ redox cycles were demonstrated to be extremely important in activating PDS to produce reactive species. The degradation pathway of nimesulide was proposed combined with the HPLC/MS spectra and DFT calculation, and the overall toxicity of nimesulide were effectively alleviated in CuFeO 2 /NPC-600+PDS system according to toxicity prediction. [ABSTRACT FROM AUTHOR]