Superstructured NiMoO4@CoMoO4 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 superstruc-tured NiMoO4@CoMoO4 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 CoMoO4 and electrochemical active NiMoO4. Moreover, this superstructured material exhibited a large gravimetric capac-itance of 1,282.2 F/g in 2 M KOH with a mass loading of 7.8 mg/cm2, leading to an ultrahigh areal capacitance of 10.0 F/cm2 that is larger than any reported values of CoMoO4 and NiMoO4 electrodes. This work provides a strategic insight for rational design of electrodes with high areal capacitances for supercapacitors.