Synthesis and Study on Ni-Co Phosphite/Activated Carbon Fabric Composited Materials with Controllable Nano-Structure for Hybrid Super-Capacitor Applications

The advantage of low resistivity and inactive binders makes binder-free electrode an excellent candidate for high-performance energy devices. A simple hydrothermal method was used to fabricate M11(HPO3)8(OH)6 (M: Ni and Co) (MHP) arrays combined with activated carbon fabric (ACF) without binder. The structures of MHP can be easily tuned from bouquets to nano-sheets by the concentration of NaH2PO2. The MHP/ACF composite materials with different structures showed the typical battery-type characteristic of anodic electrodes. In a three-electrode cell configuration, the MHP nano-sheet arrays/ACF composite has a higher capacity, of 1254 F/g, at a scan rate of 10 mA/cm2 and shows better cycling stability: 84.3% remaining specific capacity after 1000 cycles of charge-discharge measurement. The composite is highly flexible, with almost the same electrochemical performance under stretching mode. The MHP/ACF composite@ACF hybrid supercapacitor can deliver the highest energy density, of 34.1 Wh·kg-1, and a power density of 722 W·kg-1 at 1 A·g-1. As indicated by the results, MHP/ACF composite materials are excellent binder-free electrodes, candidates for flexible high-performance hybrid super-capacitor devices.

The morphology controlled growth of Co11(HPO3)8(OH)6 on nickel foams for quasi-solid-state supercapacitor applications

Co₁₁(HPO₃)₈(OH)₆ microstructures with different morphologies growing on NF were synthesized under different conditions, and the flower-like sample presents excellent electrochemical properties.

Novel nickel–cobalt phosphite with face-sharing octahedra derived electrocatalyst for efficient water splitting

Nickel–cobalt phosphite (CoNiPO) including local structural motifs with face-sharing octahedra shows excellent OER activity. The derivatized electrocatalyst (NiP₂@CoNiPO) exhibits high HER activity. DFT calculations indicated the super-exchange effect in CoNiPO can adjust local electronic structure and improve their catalytic activity.

Ni-Doped Cobalt Phosphite, Co11(HPO3)8(OH)6, with Different Morphologies Grown on Ni Foam Hydro(solvo)thermally for High-Performance Supercapacitor

Ni-doped Co₁₁(HPO₃)₈(OH)₆ with different morphologies was directly grown on Ni foam hydro(solvo)thermally under different synthetic conditions. The optimum condition is solvothermal reaction for 6 h in an ethanol/water (EW) mixed solution, the molar ratio of NaH₂PO₂/Co(NO₃)₂ being 0.5:0.1, and the obtained S0.5-6 h-EW shows three-dimensional (3D) porous nanowire bundles. Whereas in the water-only solution, microrods are obtained, suggesting that the nanowires in bundles are aggregated together via the lateral (400) direction. Long reaction time and low molar ratio of reactants are all beneficial for the lateral growth of the nanowires, and the possible formation mechanism is proposed. All the obtained Ni-doped Co₁₁(HPO₃)₈(OH)₆/Ni foam samples are directly used as supercapacitor electrodes, and S0.5-6 h-EW shows the best electrochemical performance with a specific capacity of 159 mAh g^-1 at 0.5 A g^-1, which is close to the theoretical value of 212 mAh g^-1 for Co₁₁(HPO₃)₈(OH)₆, and it is the largest reported value so far. The excellent capacitive behavior of S0.5-6 h-EW is ascribed to the 3D porous nanowire bundles directly grown on a Ni foam collector without an additive and a binder, as well as to the doping of Ni into the cobalt phosphite. The S0.5-6 h-EW//activated carbon asymmetrical supercapacitor shows a maximum energy density of 58.7 Wh kg^-1 at a power density of 532 W kg^-1 and good cycling stability with the capacity retention of 90.5% after 10 000 charging-discharging cycles at 5.5 A g^-1.

High performance electrochemical capacitor materials focusing on nickel based materials

Of the two major capacitances contributing to electrochemical storage devices, pseudo-capacitance, which results from the reversible faradaic reactions, can be much higher than the electric double layer capacitance.

High capacitive amorphous barium nickel phosphate nanofibers for electrochemical energy storage

Ba_xNi_3−x(PO₄)₂(0 <x< 3) amorphous nanofibers with excellent supercapacitive performance were synthesized through a facile cation-exchange method.

Ferric Phosphate Hydroxide Microstructures Affect Their Magnetic Properties

Uniformly sized and shape-controlled nanoparticles are important due to their applications in catalysis, electrochemistry, ion exchange, molecular adsorption, and electronics. Several ferric phosphate hydroxide (Fe4(OH)3(PO4)3) microstructures were successfully prepared under hydrothermal conditions. Using controlled variations in the reaction conditions, such as reaction time, temperature, and amount of hexadecyltrimethylammonium bromide (CTAB), the crystals can be grown as almost perfect hyperbranched microcrystals at 180 °C (without CTAB) or relatively monodisperse particles at 220 °C (with CTAB). The large hyperbranched structure of Fe4(OH)3(PO4)3 with a size of ∼19 μm forms with the "fractal growth rule" and shows many branches. More importantly, the magnetic properties of these materials are directly correlated to their size and micro/nanostructure morphology. Interestingly, the blocking temperature (T B) shows a dependence on size and shape, and a smaller size resulted in a lower T B. These crystals are good examples that prove that physical and chemical properties of nano/microstructured materials are related to their structures, and the precise control of the morphology of such functional materials could allow for the control of their performance.

A novel cobalt sodium phosphate hydroxide with the ellenbergerite topology: crystal structure and physical properties

The novel phosphate hydroxide Na_2−xCo₆(OH)₃[HPO₄][H_x/3PO₄]₃with the mineral ellenbergerite topology and alkaline cations in the framework channels shows strong antiferromagnetic interaction and magnetic transition atT_N= 44 K.

Cobalt phosphite microarchitectures assembled by ultralong nanoribbons and their application as effective electrochemical capacitor electrode materials

Cobalt phosphite (Co(11)(HPO(3))(8)(OH)(6)) microarchitectures assembled by ultralong nanoribbons are successfully synthesized by a mild hydrothermal condition without any additives. The uniform ultralong nanoribbon has a width of 100 nm and length of 20-30 μm. More importantly, Co(11)(HPO(3))(8)(OH)(6) microarchitectures are also successfully applied as an electrochemical supercapacitor with a good specific capacitance (312 F g(-1) at 1.25 A g(-1)), good rate capability and excellent cycling property (maintaining about 89.4% at 1.25 A g(-1) after 3000 cycles).