Construction of 2D ZIF-derived hierarchical and hollow NiCo-LDH “nanosheet-on-nanosheet” arrays on reduced graphene oxide/Ni foam for boosted electrochemical energy storage

Abstract 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 NiCo-LDH “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.