An ultrathin cobalt-based zeolitic imidazolate framework nanosheet array with a strong synergistic effect towards the efficient oxygen evolution reaction

Author(s): Junhui Cao ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Chaojun Lei ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Jian Yang ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Xiaodi Cheng ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Zhongjian Li ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Bin Yang ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Xingwang Zhang ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Lecheng Lei ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Yang Hou ¹ ^, ² ^, ³ ^, ⁴ ^, ⁵ , Kostya (Ken) Ostrikov ⁶ ^, ⁷ ^, ⁸

Publication date (Electronic): 2018

Journal: Journal of Materials Chemistry A

Publisher: Royal Society of Chemistry (RSC)

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Abstract

A novel ultrathin cobalt-based zeolitic imidazolate framework hybrid nanosheet array exhibits enhanced electrocatalytic activity for the oxygen evolution reaction.

Abstract

Development of highly efficient and stable zeolitic imidazolate framework (ZIF) nanosheets has recently received growing interest as alternatives to noble-metal electrocatalysts towards the oxygen evolution reaction (OER). Herein, we develop a novel vapor-phase hydrothermal growth strategy for in situ synthesis of ultrathin cobalt-based zeolitic imidazolate framework (ZIF-67) nanosheets grown on the surface of Co(OH) ₂ nanosheets vertically aligned on electrochemically exfoliated graphene (EG) foil. Ultrathin ZIF-67 nanosheets with a thickness of ∼5 nm are uniformly coated on the surface of a Co(OH) ₂ nanosheet array to form a 2D core–shell structure. Benefitting from the strong coupling and synergistic effects, the resulting EG/Co(OH) ₂/ZIF-67 hybrid exhibits excellent catalytic activity for the OER in alkaline electrolytes, which only requires an overpotential of 280 mV to attain a current density of 10 mA cm ⁻² with a low Tafel slope of 63 mV dec ⁻¹ and high stability. Such high OER performance for the EG/Co(OH) ₂/ZIF-67 hybrid is superior to that of commercial Ir/C catalysts and even better than that of all previously reported ZIF-based OER electrocatalysts. In situ Raman analyses demonstrate that under OER conditions, the Co–O species are converted into Co–OOH groups, which are responsible for the excellent catalytic activity of EG/Co(OH) ₂/ZIF-67 in the OER.