High-Activity 2D/2D Core–Shell Structure to NiMoO4-Based Electrodes for Electrochemical Energy Storage

The limited reactive active sites on the surface of NiMoO4 electrodes are the main bottleneck, restricting the rate performance of the corresponding supercapacitors (SCs). However, it is still a difficult problem to improve the utilization of redox reaction sites by adjusting the interface of the nickel molybdate (NiMoO4) electrode. This study reports a two-dimensional (2D)/2D core-shell electrode on a carbon cloth (CC) with NiMoO4 nanosheets grown on NiFeZn-LDH nanosheets (NFZ@NMO/CC). The interface of the 2D/2D core-shell structure promotes the redox reaction by improving OH- adsorption and diffusion capacity (diffusion coefficient = 1.47 × 10-7 cm2 s-1) and increasing the electrochemical active surface area (ECSA = 737.5 mF cm-2), which are much larger than the pure NiMoO4 electrode (2.5 × 10-9 cm2 s-1 and 177.5 mF cm-2). The NFZ@NMO/CC electrode exhibits an excellent capacitance of 2864.4 F g-1 at 1 A g-1 and an outstanding rate performance (92%), which is 3.18 times and 1.9 times those of the NiMoO4 nanosheets (33%) and the NiFeZn-LDH nanosheets (57.14%), respectively. Additionally, an asymmetric SC was assembled with NFZ@NMO/CC as the anode and Zn metal-organic framework (MOF)-derived carbon nanosheet (CNS)/CC as the cathode, which exhibited superior energy and power densities (70 Wh kg-1 and 709 W kg-1) with good cycling capability.