Ultrathin Metal–Organic Framework Nanosheet-Derived Ultrathin Co₃O₄ Nanomeshes with Robust Oxygen-Evolving Performance and Asymmetric Supercapacitors

Ultrathin metal-organic framework (MOF) nanosheets possessing inherent advantages of both two-dimensional (2D) features and MOFs are attracting intensive research interest. The direct manufacture of MOF nanosheets is still a challenge up to now. Here, we have developed a novel bottom-up approach to synthesize zeolitic imidazolate framework-67 (ZIF-67) nanosheets, which can be in situ converted into Co₃O₄ ultrathin nanomeshes after thermal treatment. Interestingly, the obtained Co₃O₄ nanomeshes are rich in oxygen defects, providing fruitful active sites for the faradaic reaction. The modified electrode exhibits a 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 made of Co₃O₄//activated carbon shows an energy density of 46.5 Wh kg⁻¹ at 790.7 W kg⁻¹. Furthermore, the 2D Co₃O₄ ultrathin nanomeshes show an outstanding performance for the oxygen evolution reaction with an overpotential of 230 mV at the 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.