Ionic liquid/ZIF-67 derived Co9S8-SNC catalyst for oxygen reduction reaction in alkaline electrolyte

Abstract

A series of ZIF-67-C-IL catalysts were prepared using ZIF-67 and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([BMIM]NTf₂) ionic liquid as precursors. The structure of the catalysts was characterized by XRD, TEM, SEM and XPS. The catalytic performance of the catalysts for the oxygen reduction reaction (ORR) was evaluated in a three-electrode system. The results confirmed that the high-temperature treatment of the precursors resulted in the formation of N, S co-doped carbon-encapsulated Co₉S₈ nanoparticles. To create N, S co-doped carbon coated Co₉S₈ nanoparticle catalysts, ionic liquids are used as sulfur and nitrogen sources. The catalytic activity of ORR can be improved using N, S co-doped carbon to prevent the aggregation of Co₉S₈ nanoparticles. Graphitized and N, S co-doped carbon shells are optimal for achieving high activity stability. Optimal 600-ZIF-67-C(1:1.5)-30IL catalytic activity was observed for ORR. The half-wave potential of ORR was 0.88 V vs. RHE in 0.1 mol L⁻¹ KOH, with a limit current density of 4.70 mA cm⁻². Similar ORR electrocatalytic activity was observed between this catalyst and commercial Pt/C (20 wt%).