Thermodynamic investigation of ferrocyanide/ferricyanide redox system on nitrogen-doped multi-walled carbon nanotubes decorated with gold nanoparticles

• N-MWCNTs were fabricated and “decorated” with AuNPs.
• N-MWCNTs/AuNPs were applied for study of [Fe(CN)6]3−/4− in various temperatures.
• The barrier for interfacial electron transfer decreases with temperature.
• The kinetics of charge transfer enhances with temperature.
• The AuNPs size affects the kinetic and thermodynamic parameters of [Fe(CN)6]3−/4−.

Films consisting of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) were fabricated by means of chemical vapor deposition technique with decomposition of acetonitrile. The N-MWCNTs-based films were modified with gold nanoparticles (AuNPs) with diameter either 5 or 35 nm and applied for the electrochemical investigation of ferrocyanide/ferricyanide, [Fe(CN)6]3−/4− redox system in the temperature range of 283.15–303.15 K. The findings demonstrate that on N-MWCNT films modified with AuNPs (further denoted as N-MWCNTs/AuNPs) the [Fe(CN)6]3−/4− redox system is quasi-reversible and its reversibility is improved with increasing temperature. Namely, it was established that with the rise in temperature the barrier for interfacial electron transfer decreases leading to an enhancement of kinetics of charge transfer reaction. The Gibbs free energies display that the exergonic redox process occurring on N-MWCNTs/AuNPs is shifted toward formation of [Fe(CN)6]3− with increasing temperature. With the increase of diameter of AuNPs a slight improvement of kinetics of redox process occurs.

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