Enhancement of the pseudocapacitive performance of iron hexacyanoferrate through porosity engineering: fabrication of an environment-friendly symmetric coin-cell†

In the last decade, iron hexacyanoferrate (FeHCF) or Prussian blue (PB) has become one of the most important low-cost cathode materials for supercapacitor applications due to its highly porous 3D network structure and high surface area. Presently, pure FeHCF nanocubes with two different sizes have been synthesized via a facile, easy reflux technique, wherein we have identified that pore characteristics play an important role in specific capacitance. Importantly, we have obtained the highest specific capacitance of ∼340 F g⁻¹ at a 2 mV s⁻¹ scan rate from mesoporous nanocubes. In contrast, microporous nanocubes exhibit much lower capacitance in the presence of 1.0 M Na₂SO₄ as an environment-friendly electrolyte. In addition, our study illustrates good capacitive retention (∼73%) up to 7000 cycles of operation indicating good reversibility of electrolytic ion transfer. Furthermore, we have synthesized a coin cell with an energy density of ∼4.6 W h kg⁻¹ and power density of ∼973 W kg⁻¹, which will be beneficial for high-power applications. Herein, we believe that our studies reveal the potency of FeHCF nanoparticles as an electrode material for biocompatible pseudocapacitive energy storage devices.