(485d) Molecular Simulations of Dealloying Platinum-Based Alloy Catalysts for Fuel Cells

The improvement of the catalytic efficiency for the oxygen reduction reaction (ORR) is one of the most important challenges in low-temperature fuel cell technology. Platinum is the most active element for the ORR but its high cost and scarcity hinder the commercial implementation of fuel cells in automobiles. Pt-based alloys are promising alternatives to substitute platinum while maintaining the efficiency and life-time of the pure catalyst. However, the presence of an acid medium and oxidation of the surface impact the activity and durability of the alloy catalysts through changes in its local composition. Dealloying is the selective removal of elements from an alloy. According to recent experimental reports dealloying taking place during the synthesis of ORR catalysts may yield to remarkable activity enhancement by creating characteristic porous or hollow structures. However, the dealloying process that occurs during the fuel cell operation is enhanced by the concomitant presence of oxygen that promotes metal dissolution causing the degradation of the catalyst. In this work the driving forces and the effect of dealloying on the structure of ternary alloy nanocatalysts during their synthesis and operation are studied with a multi-scale approach including density functional theory, molecular dynamics, and Kinetic Monte Carlo simulations.