Transient Microkinetic Modeling of Electrochemical Reactions: Capturing Unsteady Dynamics of CO Reduction and Oxygen Evolution

Electrochemical processes, such as water splitting and carbon dioxide/monoxide (CO(2)) reduction, will play a prominent role in the ongoing quest for mitigating climate change. For such reactions, microkinetic modeling (MKM) is a valuable tool to relate electrolyzer operating conditions, such as pH, temperature, and pressure, to current densities and faradaic efficiencies. However, previous studies have solely focused on steady-state modeling of electrochemical kinetics. Here, we perform unsteady-state MKM (USS-MKM) with and without potential sweeping to capture transient dynamics and realistically model reaction kinetics. Our analysis demonstrates that sweeping leads to accurate description of the dynamics of current-potential relationships that arise during experimental linear sweep voltammetry or staircase voltammetry measurements. The proposed approach is validated using CO reduction and oxygen evolution reactions, where reasonable agreement is observed between our long-time USS-MKM results and previously reported steady-state MKM data. We also show that our approach leads to reasonable agreement with experimental CO reduction current density data. Moreover, our proposed approach is automated, scaling to large reaction mechanisms, and enables a graphical representation of electrochemical reaction networks. Overall, by enabling USS-MKM with potential sweeping, our framework simplifies the study of complex electrocatalytic mechanisms and offers valuable insights into their operation under dynamic conditions.