▎ 摘　　要

Developing earth- abundant transition- metal based materials to efficiently catalyze the oxygen evolution reaction (OER) is an urgent demand for electrochemical water splitting and rechargeable metal- air batteries. Here, we developed a novel 3D hybrid electrocatalyst consisting of core- shell structured CoS2/ CoS2 embedded into N- doped carbon supported on electrochemically exfoliated graphene foil (EG/ CoS2/ CoS2- NC) by sulfurization treatment of EG/ Co(OH) 2/ zeolitic imidazolate framework- 67 (ZIF- 67) as precursor. The thickness of the CoS2- NC shell derived from ZIF- 67 is 10 nm and the CoS2 core generated from Co(OH) 2 nanosheet arrays has a particle size of 20 nm. Benefiting from the unique 3D core- shell structure and synergistic effects, the EG/ CoS2/ CoS2- NC hybrid enormously promotes electrocatalytic OER activity with a low overpotential of 210 mV at a current density of 10 mAcm 2 and a small Tafel slope of 61.9 mVdec 1. These values are far superior compared to the commercial Ir/ C catalyst, and even better than other reported state- of- the- art CoS2- based materials. In- situ Raman spectroscopy together with ex- situ XRD patterns reveal that the active centers of EG/ CoS2/ CoS2- NC hybrid are proven to be Co- OOH species that are derived from Co S groups during the OER process. The superb catalytic performance is also reflected in boosting electrochemical urea oxidation and hydrazine oxidation, where the accelerated oxidation reaction could be observed.