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.