Fabrication of novel FeS2 NWs/Ti3C2 cathode for Photo-Electro-Fenton degradation of sulfamethazine

Abstract

A novel pyrite nanowires (FeS2 NWs)/Ti3C2 composite with 1D-2D hybrid was developed as the cathode for efficient removal of sulfamethazine (SMT) through Photo-Electro-Fenton (PEF) mechanism. FeS2 NWs demonstrated the best PEF performance among different iron sulfide crystalline phases (pyrite, pyrrhotite and mackinawite). The FeS2 NWs/Ti3C2 (FeS2:Ti3C2 = 2:1) cathode exhibited the highest PEF degradation efficiency of 97.6% for SMT (10 mg/L) within 80 min. Diffuse reflection spectra (DRS) indicated the superior light absorption of FeS2 due to the narrow band gap, and Ti3C2 further improved the light utilization of the composite by separating the photogenerated charge carriers and broadening the light absorption region. Photocurrent and electrochemical impedance spectroscopy (EIS) demonstrated the low resistance and rapid charge transfer of FeS2 NWs. Meanwhile, the conductivity of the composite was enhanced by the introduction of Ti3C2, which was ascribed to the promoted electron migration and prolonged carrier lifetime. The FeS2 NWs/Ti3C2 cathode showed excellent recyclability of preserving 92.8% of initial performance after five cycles due to the rapid Fe3+/Fe2+ cycling. Excellent selectivity was also revealed for the FeS2 NWs/Ti3C2 cathode toward two-electron oxygen reduction reaction (ORR) pathway (n = 2.34), ensuring constant H2O2 generation. The radical scavenging experiment also demonstrated that the main oxidant in PEF system was OH. This work paves the way for the novel design and synthesis of highly efficient PEF cathodes.