NiCoSe 4 nanoparticles 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 (NiCoSe 4 /N-rGO) were fabricated using solvothermal method. The introduction of N-rGO used as a template effectively prevented agglomeration of NiCoSe 4 nanoparticles and provided more active sites, which greatly increased the electrochemical and electrical conductivity for NiCoSe 4 /N-rGO. NiCoSe 4 /N-rGO-20 presents a remarkably elevated specific capacity of 120 mA h g -1 under current density of 1 A g -1 . NiCoSe 4 /N-rGO-20 demonstrates an excellent cycle life and achieves a remarkable 83% retention rate over 3000 cycles with 10 A g -1 . NiCoSe 4 /N-rGO-20//N-rGO asymmetric supercapacitor was constructed based on the NiCoSe 4 /N-rGO-20 as an anode, N-rGO as cathode by using 2 mol l -1 KOH as an electrolyte. NiCoSe 4 /N-rGO-20//N-rGO ASC demonstrates an ultra-big energy density of 14 Wh kg -1 and good circulation stability in the power density of 902 W kg -1 . It is doubled in comparison to the NiCoSe 4 /N-rGO-20//rGO asymmetric supercapacitor (7 Wh kg -1 ). The NiCoSe 4 /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.