Thin metal organic layer derived Co/Co9S8/N,S co-doped carbon nanosheets synthesized by the space confinement effect of montmorillonite for oxygen electrocatalysis

Abstract

Highly effective bifunctional oxygen electrocatalysts play a key role in fuel cells (FCs), metal–oxygen batteries, and water splitting devices. In this paper, metal organic layer (MOL) derived Co/Co₉S₈ nanoparticles coated with N,S co-doped graphene-like carbon nanosheets were synthesized with the help of the space-confinement effect of montmorillonite (MMT). The as-prepared material shows excellent electrocatalytic activity both for oxygen reduction and oxygen evolution reactions in 0.1 M KOH solution: its ORR onset potential is 0.93 V (vs. RHE) and the limiting diffusion current density is 4.7 mA cm⁻². Moreover, the retention of current for the as-prepared material is 85% after a stability test for 10 000 s for the ORR, while those of the template free catalyst and commercial Pt/C glided below 80%. Additionally, its Tafel slope is 265 mV dec⁻¹, which is much smaller than that of the control sample, suggesting the excellent OER kinetics. The excellent catalytic activity and stability can be attributed to the relatively higher specific surface area, higher number of pyridinic-N and Co–N_x active sites, and higher graphitization degree compared to the template free catalyst.