Formation of bimetallic metal–organic framework nanosheets and their derived porous nickel–cobalt sulfides for supercapacitors

Abstract

Metal-organic frameworks (MOFs) show great advantages as new kinds of active materials for energy storage. In this study, bimetallic metal-organic frameworks (Ni/Co-MOFs) with nanosheet-assembled flower-like structures were synthesized by etching Ni-MOF microspheres in a cobalt nitrate solution. It can be clearly observed that the amount of Co(NO3)2 and etching time play crucial roles in the formation of Ni/Co-MOF nanosheets. The Ni/Co-MOFs were used as electrode materials for supercapacitors and the optimized Ni/Co-MOF-5 exhibited the highest capacitances of 1220.2 F g-1 and 986.7 F g-1 at current densities of 1 A g-1 and 10 A g-1, respectively. Ni/Co-MOF-5 was further sulfurized, and the derived Ni-Co-S electrode showed a higher specific capacitance of 1377.5 F g-1 at a current density of 1 A g-1 and a retention of 89.4% when the current density was increased to 10 A g-1, indicating superior rate capability. Furthermore, Ni/Co-MOF-5 and Ni-Co-S showed excellent cycling stability, i.e. about 87.8% and 93.7% of initial capacitance can be still maintained after 3000 cycles of charge-discharge. More interestingly, the Ni/Co-MOF-5//AC ASC shows an energy density of 30.9 W h kg-1 at a power density of 1132.8 W kg-1, and the Ni-Co-S//AC ASC displays a high energy density of 36.9 W h kg-1 at a power density of 1066.42 W kg-1. These results demonstrate that the as-synthesized bimetallic Ni/Co-MOF nanosheets and their derived nickel-cobalt sulfides have promising applications in electrochemical supercapacitors.

Hydrothermal Synthesis of Humate‐Layer‐Based Bimetal Organic Framework Composites as High Rate‐Capability and Enery‐Density Electrode Materials for Supercapacitors

“…Supercapacitors are a new generation of energy storage device that not only has high charge‐discharge efficiency, power density, reliability and long cycle lifetime similar to traditional capacitors, but also has high energy density close to batteries . In supercapacitor assemblies, electrode materials are a critical component affecting device performances.…”

“…In recent years, metal‐organic frameworks (MOFs) have attracted extensive attentions as energy storage materials, especially, supercapacitor electrode materials . MOFs are a porous crystalline material self‐assembled by coordination reactions between transition metal ions and organic ligands containing multiple carboxyl groups or nitrogen electrondonors .…”

Designing an Advanced Supercapattery Based on CuCo2S4@Ni−Mo−S Nanosheet Arrays

“…[27,28] It has been proved that the electrochemical behavior of an electrode is affected by the morphology and structure of its materials. [29,30] Accordingly, scientists introduced different types of architectures such as nanowires, [31] nanosheets, [32] and nanotubes, [33] which reflected high Cs owing to their exclusive porous networks and remarkable surface area (SA). Among which, nanosheet arrays have reflected excellent potential as desirable electrode materials for ESDs owing to their exclusive structural merits containing rich reaction sites and shortened diffusion pathways for quick charge and discharge.…”

A novel electrochemical procedure for grown of bimetallic metal–organic framework (Ni/Zn-MOF) and its derived hydroxide@C onto Ni foam as binder-free high performance battery-type electrodes for supercapacitors

“…Yang et al [20] reported synthesis of a Zndoped Ni-MOF with capacitances of 1620 and 860 F g − 1 were achieved at 0.25 and 10 A g − 1 , respectively, and the retention was kept at 91% even after 3000 cycles for MOF sample with a Zn/Ni of 0.26. Chen et al [21] have prepared bimetallic Ni/Co-MOFs with nano-sheet assembled ower-like morphology with high speci c capacitance of 1220.2 F g − 1 at 1 A g − 1 and high capacitance retention of 87.8% after 3000 cycles. Xia et al have developed a kind of Ni/Co-MOF with ake-assembled spherical microstructures, which had a capacitance of 530.4 F g − 1 at 0.5 A g − 1 and almost no capacity attenuation after 2000 charge/discharge cycles [22].…”