The slow kinetics of the oxygen reduction reaction (ORR) impede the widespread uptake of renewable energy conversion technologies such as fuel cells and water electrolysers. This talk will present some recent strategies aiming to understand and tailor the activity and stability for ORR electrocatalysts.
Model studies are suitable to investigate the ORR activity trends, understand the structure-activity-selectivity relationships and rationally design efficient nanoparticulate catalysts. We recently used Cu/Pt(111) near-surface alloys to study the ORR in alkaline electrolyte. Our results show that the ORR shares the same reaction intermediates in both acidic and alkaline electrolytes. On the other hand, we systematically studied the ORR activity and stability trends by controlling strain effects on Pt-lanthanide alloys . The active phase consists of a compressed Pt overlayer formed by leaching of the lanthanide metal. In situ grazing incidence X-ray diffraction studies on Gd/Pt(111) show that the overlayer is very stable at fuel-cell relevant potentials.
Despite the progress in the development of Pt-based electrocatalysts presenting high enhancement in ORR activity over pure Pt in RDE measurements, translating the activity enhancement to real devices remains a challenge. Recently, we have presented a gas diffusion electrode (GDE) setup which can be used for benchmarking of Pt-based electrocatalysts at fuel-cell relevant current densities (around 1 A cm-2). Our results illustrate the importance of characterising the ORR electrocatalysts under realistic conditions.