Temporal Evolution of Potential Oscillations during Ethanol Electro-Oxidation Driven by CHx Accumulation: Insights from Microkinetic Modeling

The ethanol oxidation reaction is outstanding for electrochemical energy conversion devices, which are pivotal for overcoming the challenges of the energy transition. Therefore, it is extremely important to understand the phenomena that govern the reaction kinetics to improve the performance of these devices. In this regard, using microkinetic models alongside experiments under oscillatory conditions has proven to be a promising approach. This study proposes a microkinetic model to elucidate the oscillatory dynamics of ethanol electro-oxidation on platinum in acidic medium by comparing experimental galvanostatic data with computational simulations. By coupling 16 reaction steps, the model captures time-dependent potential oscillations driven by the competitive adsorption of intermediate species such as OH_ad and carbonaceous. Simulated potential oscillations align revealing a progressive increase in oscillatory period due to due to CH_x accumulation (up to 60% surface coverage), which impedes active site regeneration. Key findings highlight high selectivity toward partial oxidation products (acetaldehyde and acetic acid), attributed to kinetically favorable pathways that avoid C-C bond cleavage. The model successfully captures key dynamic features as: progressive increase in the oscillatory period over time, surface coverage dynamics and selectivity toward partial oxidation products. These findings shed light on the reaction mechanisms and lay the groundwork for future simulations under both oscillatory and non-oscillatory conditions, with the aim of enhancing the catalytic activity of the process.