Impact of mesoporous SiO2 support for Ni/polypyrrole nanocomposite particles on their capacitive performance

Abstract

Electro-conducting polypyrrole (PPy) coated H₂N-SiO₂/Ni nanocomposite particles are prepared by a three-step process. The objective is to analyze the influence of porous functional SiO₂ support on the electrochemical performance of the prepared H₂N-SiO₂/Ni/PPy nanocomposite particles. H₂N-SiO₂ support is first prepared by a modified sol–gel method and then co-ordinated with Ni nanoparticles via an amine functionality. Finally, H₂N-SiO₂/Ni/PPy nanocomposite particles are prepared by in situ chemical oxidative polymerization of pyrrole using citric acid as a dopant. Fourier Transform IR (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the formation of co-ordinated Ni/Ni²⁺ nanoparticles and a PPy layer with almost a core–shell type morphology. The mesoporous surface structure of H₂N-SiO₂ core-particles is confirmed from the morphological study and the specific surface area gradually decreased from 496 m² g⁻¹ to 59 m² g⁻¹ following subsequent surface modification with Ni nanoparticles and the PPy layer. The ultimate nanocomposite particles had paramagnetic properties and the magnetization value is 4.8 emu g⁻¹. Comparative electrochemical performance between electrodes made from the respective PPy, Ni/PPy and H₂N-SiO₂/Ni/PPy showed the highest specific capacitance value (982.6 F g⁻¹ from cyclic voltammetry curves) for the H₂N-SiO₂/Ni/PPy nanocomposite. The H₂N-SiO₂/Ni/PPy nanocomposite electrode is fairly stable during cycling measurement. The results indicated that the use of mesoporous functional SiO₂ support remarkably improved the mechanical stability and capacitive performance of the H₂N-SiO₂/Ni/PPy nanocomposite electrode, suitable for application in energy storage devices.