In-situ growth of MnCoO hollow spheres on nickel foam as pseudocapacitive electrodes for supercapacitors.

Pseudocapacitances combining ample redox reactions and relative rapid ion and charge transport have been extensively investigated in energy storage applications. Herein, we employ a simple two-step method to synthesize MnCoO hollow spheres (MnCoO HSs), and directly grow MnCoO HSs on nickel foam (NF) to prepare MnCoO HSs/NF. The three-dimensional (3D) macroporous structure of NF offers a perfect platform for the uniform growth of MnCoO HSs and constructs interconnected charge transfer highways. The hollow structure of MnCoO exposes abundant redox active sites for energy storage, increasing the utilization rate of electroactive materials. Benefiting from the 3D macroporous structure of NF and the hollow structure of MnCoO HSs, the ion and charge transport is greatly improved. The resultant MnCoO HSs/NF electrode shows a high specific capacitance of 648.4 F g at 2 mV s in sodium sulfate electrolyte. Furthermore, the MnCoO HSs/NF//MnCoO HSs/NF symmetrical supercapacitors are fabricated, which deliver a high energy density of 37.1 Wh kg at 250.1 W kg along with outstanding cycling stability.