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

Abstract

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 metal-organic 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.