In-situ growth of MnCo₂O₄ 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 MnCo2O4 hollow spheres (MnCo2O4 HSs), and directly grow MnCo2O4 HSs on nickel foam (NF) to prepare MnCo2O4 HSs/NF. The three-dimensional (3D) macroporous structure of NF offers a perfect platform for the uniform growth of MnCo2O4 HSs and constructs interconnected charge transfer highways. The hollow structure of MnCo2O4 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 MnCo2O4 HSs, the ion and charge transport is greatly improved. The resultant MnCo2O4 HSs/NF electrode shows a high specific capacitance of 648.4 F g(-1) at 2 mV s(-1) in sodium sulfate electrolyte. Furthermore, the MnCo2O4 HSs/NF//MnCo2O4 HSs/NF symmetrical supercapacitors are fabricated, which deliver a high energy density of 37.1 Wh kg(-1) at 250.1 W kg(-1) along with outstanding cycling stability. (c) 2020 Elsevier Inc. All rights reserved.