Superstructured NiMoO@CoMoO core-shell nanofibers for supercapacitors with ultrahigh areal capacitance.

High areal capacitance for a practical supercapacitor electrode requires both large mass loading and high utilization efficiency of electroactive materials, which presents a great challenge. Herein, we demonstrated the unprecedented synthesis of superstructured NiMoO@CoMoO core-shell nanofiber arrays (NFAs) on a Mo-transition-layer-modified nickel foam (NF) current collector as a new material, achieving the synergistic combination of highly conductive CoMoO and electrochemical active NiMoO. Moreover, this superstructured material exhibited a large gravimetric capacitance of 1,282.2 F/g in 2 M KOH with a mass loading of 7.8 mg/cm, leading to an ultrahigh areal capacitance of 10.0 F/cm that is larger than any reported values of CoMoO and NiMoO electrodes. This work provides a strategic insight for rational design of electrodes with high areal capacitances for supercapacitors.