Construction of 2D ZIF-derived hierarchical and hollow NiCo-LDH nanosheet-on-nanosheet arrays on reduced graphene oxideiNi foam for boosted electrochemical energy storage

Layered double hydroxide (LDH) with tailorable lamellar structure and compositions, and largely exposed active sites has come into view as favorable electrode material for supercapacitors. Nevertheless, the poor intrinsic conductivity and serious agglomeration of pristine LDH are two obstacles that have hindered its large-scale application. To tackle these problems, in this work, hierarchical and hollow NiCoLDH nanosheet-on-nanosheet arrays grown on reduced graphene oxide (rGO) decorated nickel foam (NF) were successfully constructed through an easy two-step room-temperature synthesis. The synthesis is realized by in situ growth of a 2D Co-based zeolite imidazolate framework followed by an etching-deposition process using nickel nitrate. The resulting NiCo-LDH@rGO/NF shows very high specific capacitance (2408.8 F g(-1) at 0.5 A g(-1)), largely outperforming control NiCo-LDH/NF (1402.5 F g(-1)) and state-of-art LDH based electrodes. Besides, the asymmetric supercapacitor (ASC) fabricated from the NiCo-LDH@rGO/NF and an activated carbon (AC) electrode displays large energy density (32.2 W h kg(-1)) and excellent electrochemical durability (80.4% retention) during a long period of time (10,000 cycles), demonstrating good promise in real applications. The boosted energy storage properties are associated with the hierarchical and hollow nanosheet-on-nanosheet structure, the introduction of rGO, and the integrated electrode configuration, which endow the NiCo-LDH@rGO/NF electrode with substantial electroactive sites, rapid charge transport and abundant electron pathways. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

A NiCoLDH nanosheet-on-nanosheet array electrode with hierarchical and hollow structure was successfully synthesized through a two-step room-temperature method, showing improved specific capacitance and cycling stability. The electrode features abundant electroactive sites, rapid charge transport, and abundant electron pathways, indicating promising applications.