Carbon Dioxide Reduction Product Selectivity Under Dynamic Conditions

Electrochemical CO2RR on silver primarily produces carbon monoxide and hydrogen. There is significant discussion in the literature about enhancing CO yield under pulsed electrolysis conditions (Figure 1). However, the current understanding does not provide a theoretical explanation for this effect. In this project, we propose using the NFRA as a theoretical framework to investigate the improvement in selectivity under pulsed electrolysis conditions [1,2]. The so-called DC contribution was employed to explain the observed enhancement in CO selectivity. A simplified model was presented in [2] to elucidate the origins of this selectivity improvement. According to the model, the improvement in selectivity depends on the charge transfer coefficients of parallel reactions. The simple model does not account for frequency dependence, nor does it consider the effects of adsorbed intermediates and mass transport. These factors are currently being investigated in an extended model.

Figure 1: CO Faradaic Efficiencies (FE) at different steady state potentials (not IR-corrected) and frequency of 1 Hz. Experimental conditions: 1.5 M KHCO₃, CO₂ saturation at 25°C, and pH 7.8. Measurements were conducted using a silver rotating disc electrode at 2500 rpm. The figure demonstrates an enhancement in CO FE under dynamic conditions in the hydrogen dominated region. Based on [2]. — **Figure 1:** CO Faradaic Efficiencies (FE) at different steady state potentials (not IR-corrected) and frequency of 1 Hz. Experimental conditions: 1.5 M KHCO₃, CO₂ saturation at 25°C, and pH 7.8. Measurements were conducted using a silver rotating disc electrode at 2500 rpm. The figure demonstrates an enhancement in CO FE under dynamic conditions in the hydrogen dominated region. Based on [2].

**Figure 1:** CO Faradaic Efficiencies (FE) at different steady state potentials (not IR-corrected) and frequency of 1 Hz. Experimental conditions: 1.5 M KHCO₃, CO₂ saturation at 25°C, and pH 7.8. Measurements were conducted using a silver rotating disc electrode at 2500 rpm. The figure demonstrates an enhancement in CO FE under dynamic conditions in the hydrogen dominated region. Based on [2].

Funding: DFG, DAAD

Collaborations:

Prof. Menka Petkovska, University of Belgrade Serbia
FOR2379 Research Unit
Dr. Nebojša Nikolić, University of Belgrade Serbia

Selected recent publications:

Frontiers in Chemistry, 8(981). doi:10.3389/fchem.2020.579869

[1] 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.

[2] Miličić, T., Sivasankaran, M., Blümner, C., Sorrentino, A., & Vidaković-Koch, T. (2023) Pulsed electrolysis – explained. Faraday Discussions, 246, 179–197. doi:10.1039/D3FD00030C.