Dual-layer-structured nickel hexacyanoferrate/MnO2 composite as a high-energy supercapacitive material based on the complementarity and interlayer concentration enhancement effect.

A dual-layer composite structure composed of a metal-organic framework structure (NiHCF) with tunable open channels and typical pseudocapacitive manganese dioxide is constructed here as an electrode material for supercapacitors. This type of structure shows enhanced specific capacitance, high energy density, and excellent rate capability and stability. The specific capacitance of the composite electrode is much larger than the sum of each part, and a synergy effect of the dual-layer structure named "interlayer concentration enhancement effect" (ICE effect for short) was proposed to account for this excellent electrochemical performance.