Tuesday, 11 October 2022: 15:00
Room 302 (The Hilton Atlanta)
The low-frequency (lf) inductive features in the electrochemical impedance (EI) spectra are generally related to surface adsorption/desorption and are modelled with a series combination of inductor (L) and a resistor (R0), as proposed by Harrington et al. [1–3]. However, the origin of such features is speculative and they are seldom analyzed in terms of overpotential. In this presentation, electron-transfer reactions at the electrode-electrolyte interface in acidic medium are investigated using electrochemical impedance spectroscopy. The lf equivalent circuit (EC) parameters are analyzed as function of overpotential for three widely investigated electrochemical reactions, viz. hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR), which are not mass-transport limited, and oxygen reduction reaction (ORR), a mass-transport limited reaction. The trends in the L and R0 values for mass-transport limited ORR differ significantly from those of the other two reactions, explaining the effect of diffusion on the reaction kinetics. Overall, these trends are indicative of the role of adsorbates in the reaction mechanism, and analysis of such parameters offers significant insight on the underlying physical processes.
References
- P. Piela, R. Fields and P. Zelenay, J. Electrochem. Soc., 153(10), A1902 (2006).
- D. Priyadarshani, D. Choudhury, M. E. Joy, A. Kottantharayil and M. Neergat, J. Phys. Chem. C, 125, 27736 (2021).
- D. A. Harrington and B. E. Conway, Electrochim. Acta, 32, 1703 (1987).