Synthesis of dendritic cobalt with flower-like structure by a facile wet chemistry method as an excellent electromagnetic wave absorber.

In this study, a three-dimensional (3D) floral dendritic cobalt (FDC) consisting of layered flakes was effectively synthesized using a facile wet chemistry method. The impact of the molar amount of NaOH on the microscopic morphology, magnetic characteristics, and electromagnetic wave (EMW) absorption properties of the FDC magnetic materials was comprehensively investigated. The results revealed that the prepared FDC features primary, secondary, and multi-level branches, with the majority of secondary branches being parallel to one another. The dendrites grew closely towards the flower's center at one end, while the tips extend in various directions, forming a dendritic flower cluster. The optimal reflection loss (RL) of S3 at 9.3 GHz was -56.34 dB with a thickness of 1.89 mm, and the maximum effective absorption bandwidth (EAB, RL < -10 dB) reached 6.0 GHz (12.0-18.0 GHz) at a thickness of 1.30 mm. Consequently, the FDC magnetic materials produced in this study presented a method for fabricating high-performance electromagnetic wave absorption (EMWA) materials.

NiCoSe4nanoparticles derived from nickel-cobalt Prussian blue analogues on N-doped reduced graphene oxide for high-performance asymmetric supercapacitors.

Synthesis of NiHCCo precursors via simple co-precipitation and nickel-cobalt tetraselenide composites grown on nitrogen-doped reduced graphene oxide (NiCoSe4/N-rGO) were fabricated using solvothermal method. The introduction of N-rGO used as a template effectively prevented agglomeration of NiCoSe4nanoparticles and provided more active sites, which greatly increased the electrochemical and electrical conductivity for NiCoSe4/N-rGO. NiCoSe4/N-rGO-20 presents a remarkably elevated specific capacity of 120 mA h g-1under current density of 1 A g-1. NiCoSe4/N-rGO-20 demonstrates an excellent cycle life and achieves a remarkable 83% retention rate over 3000 cycles with 10 A g-1. NiCoSe4/N-rGO-20//N-rGO asymmetric supercapacitor was constructed based on the NiCoSe4/N-rGO-20 as an anode, N-rGO as cathode by using 2 mol l-1KOH as an electrolyte. NiCoSe4/N-rGO-20//N-rGO ASC demonstrates an ultra-big energy density of 14 Wh kg-1and good circulation stability in the power density of 902 W kg-1. It is doubled in comparison to the NiCoSe4/N-rGO-20//rGO asymmetric supercapacitor (7 Wh kg-1). The NiCoSe4/N-rGO-20//N-rGO ASC capacity retention is still up to 93% over 5000 cycles (5 A g-1). The results reveal that this device would be a prospective cathode material of supercapacitors in actual applications.