Fundamental studies on the ORR on model surfaces and High Surface Area Catalysts (HSACs)
Platinum-based electrocatalysts are still the state-of-the-art cathodes for the ORR. During the last decades, extensive investigations were performed on platinum single-crystals, in order to provide more insight into the mechanism of the ORR and the origin of the overpotential. It is well established that the activity for the ORR is strongly influenced by the presence of strongly adsorbed oxygenated species on the platinum surface, which is inseparable from the adsorption of oxygen. In our group, the investigation of the relationship between the surface coverage by oxygen and oxygenated species and the activity for ORR and other related reactions on platinum surfaces is a key subject.
High-Surface Area Catalysts (HSACs)
Carbon-supported nanoparticles can offer large surface areas and thus minimize the amount of noble material required. In addition, the use of bimetallic alloy nanoparticles can decrease the overpotential for the ORR by optimizing the surface coverage of oxygen and oxygenated species. Even though the use of nanoparticles increases substantially the Electrochemical Surface Area (ECSA) the specific activity (current normalized to real surface area) decreases. Additionally, the mechanism of degradation of platinum nanoparticles and dealloying of bimetallic structures are key issues to be resolved. In order to design active and stable electrocatalysts, the understanding of the effects in the nanoscale is a prerequisite. Towards this direction, the activity and stability of platinum and platinum-based nanoparticles is studied in the Electrocatalysis group in collaboration with the Atomistic Modelling group in our institute.