Co-catalysis of metal sulfides accelerating Fe2+/Fe3+ cycling for the removal of tetracycline in heterogeneous electro-Fenton using an novel rolled NPC/CB cathodes

Abstract

• The first study to apply NPC and CB to fabricate a novel rolled carbonaceous GDE. • Application of NPC/CB cathode in heterogeneous EF with metal sulfides as co-catalysts, the removal of the tetracycline reach 100%. • The study showed metal sulfides can accelerate the conversion of Fe 3+ to Fe 2+ by exposing reducible metal active sites. This work utilizes nitrogen-doped porous carbon (NPC) and carbon black (CB) to fabricate a novel rolled carbonaceous gas-diffusion cathode by polytetrafluoroethylene (PTFE) as adhesive, which greatly improves the production of H 2 O 2 to 7.27 mg h −1 cm −2 by optimization in near neutral pH condition. Further application of NPC/CB cathode in heterogeneous electro-Fenton (EF) experiments with synthetic pyrite (FeS 2 ) as catalyst, metal sulfides (MoS 2 , WS 2 ) as co-catalysts, the removal efficiency of the tetracycline (50 mg L −1 ) could reach 100% and the total organic carbon (TOC) removal efficiency of counterpart could reach 81.3%, respectively. Because of the FeS 2 produces H + and Fe 2+ in the presence of H 2 O 2 , which provides pH value and catalytic ion that suitable for EF. Meanwhile, the metal sulfides can accelerate the conversion of Fe 3+ to Fe 2+ by exposing reducible metal active sites on the surface of the catalysts, thus drastically increased the efficiency of H 2 O 2 decomposition and pollutant degradation, also optimized the disadvantage of little Fe 2+ leaching from FeS 2 in heterogeneous EF. Further tests of this system indicated its potential for the treatment of tannery effluents. It provided an effective and feasible scheme for promoting the improvement of the heterogeneous EF system and the development of practical application.