Honeycomb nanoarchitectonics of MnO₂/carbon-confined Fe(CN)₆^3- electrode for high capacitance and rate performance based on EDLC and dual-pseudocapacitance

MnO2, a pseudocapacitive material, is considered an important component to fabricate electrodes for aqueous supercapacitors. However, the poor conductivity and low specific capacitance (<250 F g(-1)) of MnO2 become roadblocks on the way to its more applications. Here, we demonstrate the possibility of preparing a high-performance MnO2-based electrode (OPHC-MnO2-K3Fe(CN)(6)) with MnO2/honeycomb carbon-confined K3Fe(CN)(6). The vertically aligned MnO2 nanosheets are tightly immobilized on the OPHC surface and Fe(CN)(6)(3-) adsorbs on OPHC-MnO2 interface, which ensure electrons are rapidly transported between multiple interfaces during the redox couples of Mn(IV)/Mn(III) and Fe(CN)(6)(3-)/Fe(CN)(6)(4-). The OPHC-MnO2-K3Fe(CN)(6) electrode exhibits not only electric double-layer capacitance but also pseudocapacitance derived from the redox couples of Mn(IV)/Mn(III) and Fe(CN)(6)(3-)/Fe(CN)(6)(4-), thus presenting both high capacitance and rate (332.7 and 141.1 F g(-1) at 0.5 and 100 A g(-1), respectively). More importantly, the assembled OPHC-MnO2-K3Fe(CN)(6)//OPHC-K3Fe(CN)(6) asymmetric supercapacitor provides a remarkable energy density of 75.6 Wh kg(-1) at a power density of 302.2 W kg(-1) and an outstanding cycling performance reflected by the capacitance retention of 99.6 % after 20,000 cycles. Our research opens a new avenue for designing and synthesizing versatile pseudocapacitive materials with high performance.