Nickel cobaltite nanosheets coated on metal-organic framework-derived mesoporous carbon nanofibers for high-performance pseudocapacitors.

Core-shell structured carbon nanofiber@metal oxide is one of the most promising hybrid electrodes as supercapacitors, in which the pseudocapacitive metal oxides can be fully exerted and stabilized on the carbonaceous scaffolds. However, facile fabrication of mesoporous carbon nanofibers and integration of them with metal oxides are challenging. Herein, we report a new type of mesoporous carbon nanofibers (MCNs), derived from zinc-trimesic acid fibers, acting as the scaffolds to anchor nickel cobaltite (NiCo2O4) nanosheets after surface O-functionalization. The resultant core-shell OMCN@NiCo2O4 nanostructure is demonstrated by scanning electron microscope (SEM), elemental mapping, bright-field/high-resolution transmission electron microscope (TEM), selected area electron diffraction (SAED) studies. The anchored NiCo2O4 nanosheets are dense (97.4%), and have a strong interaction with OMCN, as revealed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and H2-temperature programmed reduction (H2-TPR) techniques. As expected, the OMCN@NiCo2O4 is highly efficient, showing a high specific capacitance of 1631 F g-1 at the current density of 1 A g-1, excellent rate capability and superior cycling stability up to 5000 cycles within a high capacitance retention ratio of 94.5%. This research opens the avenue to fabricate high-efficiency carbon-metal oxide electrodes using metal-organic framework fiber-derived mesoporous carbon nanofibers and integration of them with NiCo2O4 nanosheets by increasing the interfacial interaction.

Versatile NiO/mesoporous carbon nanodisks: controlled synthesis from hexagon shaped heterobimetallic metal-organic frameworks.

Hexagonal NiO/mesoporous carbon nanodisks (NiO/MCN) are facilely and controllably synthesized via constructing nickel-zinc trimesic acid heterobimetallic metal-organic framework (HMOF) disks before pyrolysis at 910 °C. Tailoring the Ni/(Zn + Ni) feed ratio and the reaction time during the HMOF synthesis creates a well-defined hexagonal carbon nanodisk with properly populated NiO nanocrystals while maintaining high porosity and conductivity. Such an elaborately fabricated NiO/MCN is highly stable, and exhibits the largest specific capacitance of 261 F g-1 and the highest specific activity factor of 1.93 s-1 g-1 of any composite nanodisk during the capacitive test and 4-nitrophenol reduction, respectively.