Highly efficient FeS/Fe₃O₄ @ biomass carbon bifunctional catalyst with enriched oxygen vacancies for heterogeneous...

Low H₂O₂ production, narrow adaptive pH range and slow Fe(II) regeneration on the cathode still limit efficiency of electro-Fenton (EF) and its application. Herein, we designed a bifunctional catalyst with FeS and Fe₃O₄ nanoparticles dispersed on porous carbon (CFeS@C) using template of sodium alginate (SA)/FeSO₄ hydrogel mixed with carbon black (CB), which presented high H₂O₂ generation efficiency and outstanding tetracycline degradation efficiency under wide pH ranges (3-8) with a low energy consumption of 19.6 kWh/kg total organic carbon (TOC). The introduction of CB created abundant oxygen vacancies in CFeS@C, promoting the oxygen adsorption and the electrochemical generation of H₂O₂, which further boosted the formation of ^•OH due to the interaction with Fe²⁺ on the cathode surface. Simultaneously, the reaction between the outer layer of FeS and Fe³⁺ not only accelerated iron cycling but also reduced the solution pH. It was verified that ^•OH and ¹O₂ played a dominant role in organics degradation. The system maintained stability after 10 cycles and effectiveness in the treatment of pharmaceutical wastewater. This study would offer a new strategy to develop an efficient and durable bifunctional catalyst for heterogeneous EF system working in wide pH conditions for wastewater treatment.