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Zeolitic Imidazolate Framework‐Derived Core‐Shell‐Structured CoS 2 /CoS 2 ‐N‐C Supported on Electrochemically Exfoliated Graphene Foil for Efficient Oxygen Evolution
Author(s) -
Cao Junhui,
Lei Chaojun,
Yang Bin,
Li Zhongjian,
Lei Lecheng,
Hou Yang,
Feng Xinliang
Publication year - 2019
Publication title -
batteries and supercaps
Language(s) - English
Resource type - Journals
ISSN - 2566-6223
DOI - 10.1002/batt.201800098
Subject(s) - overpotential , tafel equation , oxygen evolution , nanosheet , electrocatalyst , graphene , materials science , catalysis , electrochemistry , imidazolate , transition metal , chemical engineering , inorganic chemistry , chemistry , nanotechnology , electrode , organic chemistry , engineering
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 CoS 2 /CoS 2 embedded into N‐doped carbon supported on electrochemically exfoliated graphene foil (EG/CoS 2 /CoS 2 ‐NC) by sulfurization treatment of EG/Co(OH) 2 /zeolitic imidazolate framework‐67 (ZIF‐67) as precursor. The thickness of the CoS 2 ‐NC shell derived from ZIF‐67 is 10 nm and the CoS 2 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/CoS 2 /CoS 2 ‐NC hybrid enormously promotes electrocatalytic OER activity with a low overpotential of 210 mV at a current density of 10 mA cm −2 and a small Tafel slope of 61.9 mV dec −1 . These values are far superior compared to the commercial Ir/C catalyst, and even better than other reported state‐of‐the‐art CoS 2 ‐based materials. In‐situ Raman spectroscopy together with ex‐situ XRD patterns reveal that the active centers of EG/CoS 2 /CoS 2 ‐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.