Oxygen Reduction Reaction Kinetic Model Discrimination

The kinetics of ORR is perhaps one of the most studied topics in electrochemistry. However, there is still no full understanding of this reaction. In terms of a mechanistic analysis of the ORR, the major difficulty lies in the fact that the ORR is a complex process involving the transfer of up to 4 electrons. Consequently, different kinetic schemes can be formulated for this reaction. Discrimination between these kinetic variants is difficult, especially if only steady-state conditions are considered. In this project ORR on silver was studied with a help of NFRA. Silver is an interesting ORR catalyst with technical applications in chloralkali electrolysis or metal-air batteries. To explain the nonlinear ORR dynamics, we proposed two models: a simple one including the first electron transfer and oxygen diffusion [1-4,5] and a more complex one including four steps and diffusion [5]. Both models were able to explain the steady-state and linear dynamic data well (Figure 1). The distinction between the models was made possible by analysing the nonlinear part of the dynamic response [5].

Figure 2: The experimental and simulated magnitudes of the first-order Frequency Response Function (FRF) on the left and the second-order FRF on the right for the Oxygen Reduction Reaction (ORR) on a silver rotating disc electrode in 11 M NaOH at 60°C, 0.9 V RHE, and 1600 rpm. Experimental data are depicted as symbols, while model data are represented by lines in various colors. The figure illustrates that model discrimination is not feasible using only the first-order FRF (linear frequency response, EIS). In contrast, the second-order FRF (nonlinear analysis) demonstrates a higher capability for model discrimination. Based on [5]. — **Figure 2**: The experimental and simulated magnitudes of the first-order Frequency Response Function (FRF) on the left and the second-order FRF on the right for the Oxygen Reduction Reaction (ORR) on a silver rotating disc electrode in 11 M NaOH at 60°C, 0.9 V RHE, and 1600 rpm. Experimental data are depicted as symbols, while model data are represented by lines in various colors. The figure illustrates that model discrimination is not feasible using only the first-order FRF (linear frequency response, EIS). In contrast, the second-order FRF (nonlinear analysis) demonstrates a higher capability for model discrimination. Based on [5].

**Figure 2**: The experimental and simulated magnitudes of the first-order Frequency Response Function (FRF) on the left and the second-order FRF on the right for the Oxygen Reduction Reaction (ORR) on a silver rotating disc electrode in 11 M NaOH at 60°C, 0.9 V RHE, and 1600 rpm. Experimental data are depicted as symbols, while model data are represented by lines in various colors. The figure illustrates that model discrimination is not feasible using only the first-order FRF (linear frequency response, EIS). In contrast, the second-order FRF (nonlinear analysis) demonstrates a higher capability for model discrimination. Based on [5].

Funding: DFG

Collaborations

Prof. Menka Petkovska, University of Belgrade Serbia
FOR2379 Research Unit
Asst. Prof. Tobias K. S. Ritschel, DTU, Denmark

Selected recent publications

[1] Kandaswamy, S., Sorrentino, A., Borate, S., Živković, L.A., Petkovska, M., and Vidaković-Koch, T. (2019) Oxygen reduction reaction on silver electrodes under strong alkaline conditions. Electrochimica Acta, 320, 134517. doi:10.1016/j.electacta.2019.07.028

[2] Živković, L.A., Vidaković-Koch, T., and Petkovska, M. (2020) Computer-Aided Nonlinear Frequency Response Method for Investigating the Dynamics of Chemical Engineering Systems. Processes, 8(11), 1354. doi.org/10.3390/pr8111354

[3] Živković, L.A., Kandaswamy, S., Petkovska, M., and Vidaković-Koch, T. (2020) Evaluation of Electrochemical Process Improvement Using the Computer-Aided Nonlinear Frequency Response Method: Oxygen Reduction Reaction in Alkaline Media. Frontiers in Chemistry, 8(981). doi:10.3389/fchem.2020.579869

[4] Vidaković-Koch, T., Miličić, T., Živković, L. A., Chan, H. S., Krewer, U., & Petkovska, M. (2021) Nonlinear frequency response analysis: a recent review and perspectives. Current Opinion in Electrochemistry, 30, 100851. doi:10.1016/j.coelec.2021.100851.

[5] Živković, L. A., Kandaswamy, S., Sivasankaran, M., Al-Shaibani, M. A. S., Ritschel, T. K. S., & Vidaković-Koch, T. (2023) Nonlinear frequency response analysis of oxygen reduction reaction on silver in strong alkaline media. Electrochimica Acta, 451, 142175. doi:10.1016/j.electacta.2023.142175.