Polymer electrolyte membrane fuel cells (PEMFCs) are a promising alternative technology to internal combustion engines used on vehicles. However, improvements on durability and performance are needed in order to boost the commercialization of this technology. The oxygen reduction reaction (ORR) is the greatest source of voltage losses, and several studies have identified that the catalyst degradation on the cathode is the main contributor to the loss of electrochemical surface area (ECSA). Therefore, understanding degradation pathways in the ORR kinetics and the activity of the catalyst layer (CL) are a priority for improving the performance and durability of PEMFC.

Three well-known phenomena occur in the oxygen electrochemistry on platinum catalyst:​ i) oxygen reduction reaction (ORR), ii) platinum oxide growth and iii) peroxide formation. Many of the elementary steps are common to the three reaction pathways, even though, the kinetics of these mechanisms are usually modelled separately. This MSc thesis first analyzes and studies novel unified micro kinetic models on ORR available in the literature. Then, it derives and implements a new ORR kinetic model that depends only on the activation and adsorption energies. Kinetic parameters were estimated by fitting the model to Pt electrode experimental data. Comparison between experimental data and proposed model as well as other models show that the model is able to capture key steady state characteristics of the ORR, and some transient trends.