Direct atomic-level insight into oxygen reduction reaction on size-dependent Pt-based electrocatalysts from density functional theory calculations

Developing novel oxygen reduction reaction (ORR) catalysts with high activity is urgent for proton exchange membrane fuel cells. Herein, we investigated a group of size-dependent Pt-based catalysts as promising ORR catalysts by density functional theory calculations, ranging from single-atom, nanocluster to bulk Pt catalysts. The results showed that the ORR overpotential of these Pt-based catalysts increased when its size enlarged to the nanoparticle scale or reduced to the single-atom scale, and the Pt38 cluster had the lowest ORR overpotential (0.46 V) compared with that of Pt111 (0.57 V) and single atom Pt (0.7 V). Moreover, we established a volcano curve relationship between the ORR overpotential and binding energy of O* (ΔEO*), confirming the intermediate species anchored on Pt38 cluster with suitable binding energy located at top of volcano curve. The interaction between intermediate species and Pt-based catalysts were also investigated by the charge distribution and projected density of state and which further confirmed the results of volcano curve.