The Oxygen Reduction Reaction on Pt: Why Particle Size and Inter-particle Distance Matter

Carbon supported Pt based nanoparticles are important electrocatalysts for energy conversion reactions such as the oxygen reduction reaction (ORR). Although this reaction has been extensively studied, the influence of factors such as the particle size and inter-particle distance of the nanoparticle-based or nano-sized electrocatalysts on the ORR activity and durability are not yet fully understood and often intertwined. This lack of understanding is mostly based on the limitation in the synthetic approaches of the electrocatalysts which usually do not allow an independent variation of particle size and inter-particle distance. In the presented work, we succeeded to disentangle both factors using a “colloidal toolbox” approach and have demonstrated an effect of the inter-particle distance on the electronic properties of the nanoparticle via operando electrochemical X-ray absorption spectroscopy (XAS).