Reduced core-shell structured MnCo2O4@MnO2 nanosheet arrays with oxygen vacancies grown on Ni foam for enhanced-performance supercapacitors

In this work, reduced core-shell structured MnCo2O4@MnO2 (rMnCo(2)O(4)@rMnO(2)) nanosheet arrays with appropriate oxygen vacancies grown on Ni foam have been prepared via a two-step hydrothermal process with facile annealing and NaBH4 solution treatment. The good designs of 2D-2D MnCo2O4@MnO2 core-shell nanosheet arrays and in situ introduce of oxygen vacancies provide abundant reactive sites and effective electronic transmission, endowing the rMnCo(2)O(4)@rMnO(2) an excellent electrochemical performance. And the rMnCo(2)O(4)@rMnO(2)-2h electrode exhibits an aerial capacitance of 3.39 F cm(-2) (or 0.4 mA h cm(-2)) at the current density of 3 mA cm(-2), much higher than those of MnCo2O4 (1.27 F cm(-2), or 0.15 mA h cm(-2)) and MnCo2O4@MnO2 (1.89 F cm(-2), or 0.22 mA h cm(-2)). Also, the electrode possesses pretty rate performance of 1.66 F cm(-2) (or 0.19 mA h cm(-2)) at 60 mA cm(-2) and cycling property with 92.5% capacity retention after 3000 cycles. Furthermore, the assembled rMnCo(2)O(4)@rMnO(2)-2h//AC asymmetric supercapacitor yields an energy density of 32.4 Wh kg(-1) at a power density of 904.9 Wkg(-1), 27.3 Wh kg(-1) even at 4524.2Wkg(-1) and maintains 81.8% of initial capacitance at 50 mA cm(-2) after 5000 cycles, which indicate the rMnCo(2)O(4)@MnO2-2h should be applicable electrode materials for supercapacitors. (C) 2020 Elsevier B.V. All rights reserved.