NiCo Layered Double Hydroxide Nanoarrays Grown on an Etched Ni Foam Substrate for High-Performance Supercapacitor Electrode

Nickel foam (NF) with a desirable 3D open-pore structure is extensively adopted in developing integrated electro-des, and the enhanced interaction between the electrode materials and NF substrate is recognized as an effective method for a high-performance supercapacitor electrode with a low resistance nature and high stability. In this work, an etched NF (ENF) with residual nanosheets is adopted as a novel substrate to facilitate the capacitive activity of NiCo layered double hydroxide (NiCo LDH) nanowire arrays. NiCo LDH nanosheet arrays grown on a pristine NF substrate (NiCo LDH/NF) are synthesized initially and used as a precursor. Then, the ENF substrate with a residual nanosheet is obtained by partially removing NiCo LDH nanosheet arrays in a formamide/KOH mixed solution. Subsequently, NiCo LDH nanowire arrays are hydrothermally grown on ENF to form a NiCo LDH/ENF electrode. The role of the residual nanosheet on ENF is discussed in detail, in which the content of Ni3+/Co3+ and the resistance nature of NiCo LDH/ENF can be optimized with the amount of residual nanosheets. Hence, the ENF substrate with an optimal amount of residual nanosheets is beneficial for retaining the adhesion of nanoarrays and realizing the low resistance nature in a mild route. The NiCo LDH/ENF electrode shows a capacity of 976.6 C g-1 at 1 A g-1 with excellent cyclic stability. The as -assembled NiCo LDH/ENF//activated carbon hybrid supercapacitor delivers a high specific capacitance of 150.8 F g-1 at 1 A g-1 and achieves an energy density of 67.9 Wh kg-1 at a power density of 900 W kg-1 with an excellent cycle stability with a 90.6% capacity retention after 10,000 cycles, indicating high energy density and good stability.