Facet-controlled morphology of cobalt disulfide towards enhanced oxygen reduction reaction

Abstract

Catalytic activity has a significant contribution from exposed facets which are prominently correlated with morphology. It has been witnessed that even a small refinement in morphology alters the catalytic activity over several folds which is a key towards catalyst design. The present study thereby explores the design of octahedral CoS₂ crystals with the aim of exposing highly active facets for the oxygen reduction reaction (ORR) which were carefully synthesized to incorporate carbon inherently. One-pot hydrothermal synthesis was employed using trisodium citrate and sodium thiosulfate. The resultant crystals of octahedral CoS₂ with exposed {111} and {220} planes were revealed by HR-TEM and XRD studies. Detailed structure–activity insight regarding ORR was obtained using rotating ring disk electrode and electrochemical quartz crystal microbalance (EQCM) analysis and facet controlled octahedral CoS₂ was shown to have the 50 fold increase in activity relative to other variants in an acidic medium and is comparable to a state-of-the-art Pt/C (20%) catalyst. The local catalytic activity of the CoS₂ catalyst was visualized by the redox-competition mode of scanning electrochemical microscopy (RC-SECM).