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Energy, Environmental, and Catalysis Applications
Ultrathin Metal-Organic Framework Nanosheets Derived Ultrathin Co3O4 Nanomeshes with Robust OxygenEvolving Performance and Asymmetric Supercapacitors Guijuan Wei, Zhen Zhou, Xixia Zhao, Weiqing Zhang, and Changhua An ACS Appl. Mater. Interfaces, Just Accepted Manuscript • Publication Date (Web): 27 Jun 2018 Downloaded from http://pubs.acs.org on June 27, 2018
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ACS Applied Materials & Interfaces
Ultrathin
Metal-Organic
Framework
Nanosheets
Derived Ultrathin Co3O4 Nanomeshes with Robust Oxygen-Evolving
Performance
and
Asymmetric
Supercapacitors Guijuan Wei,a,c Zhen Zhou,c Xixia Zhao,c Weiqing Zhang,b and Changhua An a, b, c *
a
Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion,
School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (P.R. China) b
Tianjin Key Laboratory of Advanced Functional Porous Materials, Institute for New
Energy Materials & Low-Carbon Technologies, Tianjin University of Technology, Tianjin 300384, China. c
College of Science, and College of Chemical Engineering, China University of
Petroleum, Qingdao 266580 (P.R. China) KEYWORDS: 2D MOF, cobalt oxide, oxygen evolution, supercapacitor
ABSTRACT
Ultrathin metal-organic framework (MOF) nanosheets possessing inherent advantages of both 2-dimensional (2D) features and MOFs, are attracting intensive research interests. The direct manufacture of MOF nanosheets is still a challenge up to date. Here we have developed a novel bottom-up approach to synthesize zeolitic
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imidazolate framework-67 (ZIF-67) nanosheets, which can be in-situ converted into Co3O4 ultrathin nanomeshes after thermal treatment. Interestingly, the achieved Co3O4 nanomeshes are rich in oxygen defects, providing fruitful active sites for Faradaic reaction. The modified electrode exhibits large specific capacitance (1216.4 F g−1 at 1 A g−1), as well as a high rate capability (925.5 F g−1 at 20 A g−1). Moreover, an asymmetric supercapacitor (ASC) made of Co3O4//AC shows energy density of 46.5Wh kg-1 at 790.7 W kg-1. Furthermore, the 2D Co3O4 ultrathin nanomeshes show outstanding performance for oxygen evolution reaction (OER) with an overpotential of 230 mV at onset potential and a small Tafel slope of 74.0 mV dec−1. The present method presents a facile avenue to the preparation of other 2D ultrathin metal oxide nanostructures with various applications in energy catalysis and conversion.
INTRODUCTION Metal-organic frameworks (MOFs) have been attractive for gas adsorption and separation, new energy production, and catalysis, due to their tunable structure with high surface areas, and well-developed pores.1-3 In the past few years, the control over the shaped MOFs with different dimensions has been a hot topic in order to optimize their performances. 2-dimensional (2D) ultrathin MOF nanosheets have been received increasing attention in the field of the new energy production.4,
5
Their inherent
advantages include: (i) nanoscale sheets allow rapid mass transport and superior electron transfer; (ii) enhanced well-defined interfaces between the electrolyte and electrode ensure the fast charge transfer along 2D basal planes, consequently 2 ACS Paragon Plus Environment
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ACS Applied Materials & Interfaces
enhancing the catalytic performance; (iii) highly open structures make extremely high percentages of exposed surface atoms, which possess coordinately unsaturated metal sites to give high catalytic activity. To date, top-down (delamination of bulk MOFs) and bottom-up methods (direct growth of 2D MOF nanosheets from solution) can be used to prepare 2D MOF nanosheets. The former one is facile and efficient to weaken the interlayer force in MOFs by the sonication or shaking operation.6-8 However, it is not viable to synthesize high quality MOF nanosheets on a large scale (the yield
