Ni Prussian Blue Analogue/Mesoporous Carbon Composite as Electrode Material for Aqueous K-Ion Energy Storage: Effect of Carbon-Framework Interaction on Its Electrochemical Behavior

This study evaluates the interaction of mesoporous carbon (MC) and nitrogen doped mesoporous carbon (NMC) with Nickel prussian blue analogues (Ni-PBA) and its effect on electrochemical properties and energy storage. The Raman, IR, Mossbauer and XPS results reveal that MC-NiPBA composite exhibited a large modification to covalent character of carbon and an increase in defects of carbonaceous material. This latter is associated with the oxidation of carbon sites and reduction of iron in hexacyanoferrate during composite synthesis, which increase the charge subtraction in Fe (Low Spin) through CN ligand, due to sp-d hybridization between nickel and carbon structure. Electrochemical impedance spectroscopy characterization showed that the interaction between MC and NiPBA decreases the paste resistance and improves the chemical capacitance of the material, whereas, the apparent diffusion coefficient for K-ion in Ni-PBA is not affected by the presence of mesoporous carbon. The cyclic voltammetry and galvanostatic characterization confirm the enhancement of MC-NiPBA capacitance during charge/discharge process due to their synergetic interaction. However, the donor/acceptor characteristics of nitrogen modify the orbital hybridization in doped carbon, inhibiting the carbon-framework interaction.