Synthesis and characterization of two-faced brush-like MXene anchored NiCo-LDH electrode for high-performance supercapacitors

Layered nickel‑cobalt double hydroxide (NiCo-LDH) with a high theoretical charge storage capacity has great potential to be used as a supercapacitor (SC) electrode. However, its low electronic conductivity, low stability, and aggregation tendency has been recognized as the main drawbacks. Herein, solvent-induced interfacial-confined process was used to synthesize an unusual brush-like heterostructure of NiCo-LDH vertically anchored on conductive MXene nanosheets, enabled by the solvent-induced effect of the polar hydroxyl group of ethylene glycol and the limited domain effect of MXene nanosheets. This unique brush-like structure promoted mass transfer and improves charge transport behaviours compared to the pure NiCo-LDHs. The resultant NiCo-LDH@MXene had an ideal larger peak pore size of 3.8 nm and BET specific surface area of 175.13 m2 g−1 compared to those of NiCo-LDH, which facilitates the exposure of active sites and mass transfer. In three-electrode configuration, NiCo-LDH@MXene provided a significant specific capacity of 1310 F g−1 at a 1 A g−1 current density. At a power density of 699.1 W kg−1, NiCo-LDH@MXene showcased a substantial energy density of 73.8 Wh kg−1 in a symmetric supercapacitor. At a 6 A g−1 current density, NiCo-LDH@MXene-based SC could retain 92.5% of its capacitance at the end of 10,000 charge and discharge cycles, underscoring its excellent stability in practical application. Electrochemical tests and DFT simulation further revealed enhanced ionic adsorption/transport and electron transport, more enriched active sites, and altered electrical configuration on account of the lower energy barrier for NiCo-LDH@MXene relative to NiCo-LDH. The synthesis route and the insights reported here pave a way toward advanced electrode design and development.