A facile synthesis of FeS/FeC nanoparticles highly dispersed on grown N-doped CNTs as cathode electrocatalysts for microbial fuel cells.

A novel composite of iron sulfide, iron carbide and nitrogen carbides (Nano-FeS/FeC@NCNTs) as a cathode electrocatalyst for microbial fuel cells (MFCs) is synthesized by a one-pot solid state reaction, which yields a unique configuration of FeS/FeC nanoparticles highly dispersed on grown nitrogen-doped carbon nanotubes (NCNTs). The highly dispersed FeS/FeC nanoparticles possess large active sites, while the NCNTs provide an electronically conductive network. Consequently, the resultant Nano-FeS/FeC@NCNTs exhibit excellent electrocatalytic activity towards the oxygen reduction reaction (ORR), with a half-wave potential close to that of Pt/C (about 0.88 V RHE), and enable MFCs to deliver a power density of 1.28 W m after two weeks' operation, which is higher than that of MFCs with Pt/C as the cathode electrocatalyst (1.02 W m). Theoretical calculations and experimental data demonstrate that there is a synergistic effect between FeC and FeS in Nano-FeS/FeC@NCNTs. FeC presents a strong attraction and electron-donating tendency to oxygen molecules, serving as the main active component, while FeS reduces charge transfer resistance by transferring electrons to FeC, synergistically improving the kinetics of the ORR and power density of MFCs.