Abstract
Identifying the influence of the step defects is crucial for the development of high-performance Pt-based catalysts towards oxygen reduction reaction (ORR). To this end, intense research based on the oxygen adsorption energy (Eads(O)) criterion has been carried out for Pt single crystals, yet hardly can these studies be applied to the alloy system, considering the strain and ligand effects. Here we demonstrated that for a typical alloy (that is Pt1.2Cu octahedron), the activity is in positive correlation with the number of steps which, however, are detrimental to ORR as determined by the Eads(O) results. Using a combination of kinetics and electron density differences calculations, a novel “hydrogen activation” pathway is put forward. It is shown that the step-edge atoms can apply a repulsive force on the adsorbed hydrogen atoms, which reduces the energy barrier of the rate-determining oxygen hydrogenation process by 0.1 eV compared with the corresponding smooth surface and eventually accelerates the ORR kinetics.
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