Prussian blue analogue derived low-crystalline Mn2O3/Co3O4 as high-performance supercapacitor electrode

Metal oxide-based supercapacitors have been widely studied due to their high theoretical specific capacitance. Among many preparation methods of metal oxides, the annealing treatment of metalorganic frameworks (MOFs) has unique advantages in designable and well-controlled structure, and this approach is regarded to be suitable for preparing the metal oxides with high crystallinity. At present, it is still a great challenge to obtain low-crystalline MOFs-derived metal oxides. In this study, we have skillfully taken advantage of polyvinyl pyrrolidone (PVP) in Mn-based Prussian blue analogue (PBA) and formed the low-crystalline Mn2O3/Co3O4 composite by an annealing process. The presence of PVP can weaken the crystallization of metal oxides during the annealing process and create structural disorder. The as-prepared low-crystalline Mn2O3/Co3O4 has an excellent specific capacitance of 478.7 F g(-1) at a current density of 1 A g(-1), which is 131.7% higher than the high-crystalline counterpart. Moreover, this material exhibits outstanding cycling stability (116.4% capacitance retention after 2500 cycles). The asymmetric supercapacitor consisting of low-crystalline Mn2O3/Co3O4 as the positive electrode and nitrogen-doped graphene hydrogel as the negative electrode delivers an energy density of 32.8 Wh kg(-1) at a power density of 1190.1 W kg(-1). The superior electrochemical performances are mainly ascribed to the formation of low-crystalline Mn2O3/Co3O4 that provides more reversible active sites and accelerates ion diffusion. It is expected to open up a new avenue to the preparation of low-crystalline metal oxides for electrochemical energy storage. (C) 2020 Elsevier B.V. All rights reserved.