Surface-structure sensitive chemical diffusivity and reactivity of CO adsorbates on noble metal electrocatalysts

The electrooxidation of carbon monoxide is a typical example of structure sensitivity in electrocatalysis for fuel cells. Understanding the structure sensitivity is crucial in designing highly efficient catalysts and elucidating reaction mechanisms. Conventionally, only the reactivity of active sites was considered and optimized. However, how the reactant chemically moves to the active site has not been well studied. In this work, we found that CO ad hopping is a general phenomenon on noble metal surfaces such as platinum, iridium, rhodium, and palladium in the case of CO monolayer electrooxidation. Differences in the performances of CO ad stripping on platinum nanoparticles with different surface structures reveal that the CO ad hopping rate is structure sensitive as well. Assisted by a diffusion modeling and density functional theory calculations, it is demonstrated that the structure sensitivity is as a result of a compromise between CO ad chemical diffusivity and reactivity with OH ad .