Simulations of the Electrochemical Oxidation of Pt Nanoparticles ofVarious Shapes

The activity and stability of a platinum nanoparticle (NP) are not onlyaffected by its size but additionally depend on its shape. To this end, simulations canidentify structure-property relationships to make a priori decisions on the mostpromising structures. While the activity is routinely probed by electronic structurecalculations on simplified surface models, modeling the stability of NP model systemsin electrochemical reactions is challenging due to the long time scale of relevantprocesses such as oxidation beyond the point of reversibility. In this work, a routinefor simulating electrocatalyst stability is presented. The procedure is referred to asGREG after its main ingredientsxe0d5;a grand-canonical simulation approach usingreactive forcefields to model electrochemical reactions as a function of the galvanic cell potential. The GREG routine is applied tostudy the oxidation of 3 nm octahedral, cubic, dodecahedral, cuboctahedral, spherical, and tetrahexahedral platinum NPs. Theoxidation process is analyzed using adsorption isobars as well as interaction energy heat maps that provide the basis for constructingelectrochemical phase diagrams. Onset potentials for surface oxidation increase in the sequence cube approximate to dodecahedron <= octahedron <= tetrahexahedron < sphere < cuboctahedron, establishing a relationship between the oxidation behavior and the surface facetstructure. The electrochemical results are rationalized using structural and electronic analyses