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Abstract:
A novel, template-assisted synthesis strategy for producing hollow polypyrrole (PPy) nanoparticles (H-PPy) with an average diameter of ≈70 nm is reported. Unlike conventional methods, the approach uniquely exploits an in situ reaction between FeCl3 and CaCO3 to simultaneously generate Fe(OH)3 nanoparticles that act as dynamic, self-decomposing templates for PPy deposition. This concurrent template formation and polymer growth restricts Fe(OH)3 particle size via rapid PPy surface encapsulation, facilitating the formation of uniformly dispersed PPy-coated Fe(OH)3 particles (T-PPy). Subsequent removal of unreacted CaCO3 and Fe(OH)3 yields hollow PPy nanoparticles (H-PPy) with a 30% size reduction due to contraction of the soft PPy, resulting in a high surface area morphology. The H-PPy exhibits excellent electrochemical performance as a cathode material in both pouch-type and all-solid-state asymmetric electrochemical capacitors. The specific capacitance of H-PPy calculated by using three electrode electrochemical cell is found to be 158.2 Fg−1 at 1 Ag−1 which is much higher than that of bulk PPy and T-PPy. Areal capacitances of 40.2 and 9.6 mF cm−2 at 0.2 mA cm−2 are obtained for the pouch and solid-state cells, respectively, where activated carbon electrodes are used as anode. The pouch cell demonstrates remarkable cycling stability, retaining 104.6% of its initial capacitance after 15 000 cycles