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).
