High-performance oxygen reduction electrocatalysts derived from bimetal-organic framework and sulfur-doped precursors for use in microbial fuel cells

Abstract

Development of platinum -free cathode electrocatalysts with high oxygen reduction reaction (ORR) activity for use in microbial fuel cells (MFCs) is challenging. The current study reports a cathode electrocatalyst with high oxygen reduction reaction produced by pyrolysis of sulfur-doped Co–Zn Bi-MOF precursors. SEM, TEM, FTIR and XPS findings showed that sulfur heteroatoms were successfully coated on the Co-ZIF-8, and a carbon material with a core-shell structure (Co–S shell) was synthesized. Presence of initial Zn creates spatial isolation of Co that prevents it from sintering during pyrolysis, and Zn evaporation increases the surface area of the resulting catalysts. Atomically Co site distributed catalysts with ideal chemical and structural properties exhibit high activity and stability for the ORR in acidic media (E 1/2 = 0.75 V vs. RHE) and alkaline media (E 1/2 = 0.8 V vs. RHE) as shown by analysis of the effect of S doping contents. MFCs devices coupled with Co–N/S–C-3.5 cathode showed high open-circuit potentials (E OCV = 0.61 V) and high power densities (1190 ± 10 mW m −2 ). • A new Co–N/S–C-3.5 catalyst derived from ZIF-67 is used in MFC. • Sulfur atoms are distributed on the surface of the polyhedron to form a core-shell structure. • The doping of sulfur is beneficial to the activity of the catalyst. • The catalyst exhibits good durability in all pH mediums. • The Co–N/S–C-3.5 exhibited much higher practicability than that of Pt/C.