Structural Screening and Design of Platinum Nanosamples for Oxygen Reduction

Nanocatalyst-by-design promises to empower the next generation of electrodes for energy devices. However, current numerical methods consider individual and often geometrical closed-shell nanoparticles, neglecting how the coexistence of several and structurally diverse isomers in a sample affect the activity of the latter. Here, we present a multiscale numerical approach to calculate, in a fast and high-throughput fashion, the current density and mass activity of individual isomers, as well as predict the activity of morphologically diverse but size-selected samples. We propose specific design rules of platinum nanosamples for the electrochemical reduction of molecular oxygen, identifying the size range up to 5.5 nm as the one where isomerization of individual nanoparticles and the morphological composition of the sample cannot be neglected. We confirm a peak of the activity of defected and concave polyhedra at 2-3 nm while spherical but amorphous isomers become the most active in the range of 3-5 nm, with an astonishing mass activity of 2.7 A/mg. We provide a possible explanation to rationalize the discrepancies in the measured mass activity of size-selected samples, in terms of the different distributions of Pt isomers in each specimen.