(334e) Dft Investigation On The Stability Of Pt Clusters On Carbon Supports

A common anode catalyst used in a proton exchange membrane (PEM) fuel cell is platinum on a carbon support. The performance of the fuel cell can be enhanced by well-dispersed, stable platinum nanoparticles. One of the causes for the loss of activity in a fuel cell (as well as in other catalytic processes) is the growth, or sintering, of the nanoparticles. We suggest that the structural stability of nm-sized platinum catalyst particles can be enhanced by increasing the interaction of the nanoparticles with the carbon support, relative to the Pt-Pt interactions. In an effort to increase the interaction between the metal and the support, carbon substituted boron defects were introduced in graphite, and the adsorption energies of the metal clusters at absolute zero were estimated to be substantially higher when compared to pristine carbon using first-principles density functional theory (DFT) calculations. The adsorption energies of the metal clusters on oxidized and hydroxylated pristine and boron-doped graphite were also studied. The potential energy surface of the pristine and boron-doped carbon was scanned with a Pt atom and the activation barrier for its diffusion on the surfaces was estimated. The dynamics of Pt and Ru atoms on pristine and boron-doped graphite were studied at elevated temperatures with and without an external electric field using ab-initio molecular dynamics (AIMD) simulations and the mean square displacement of the metal atoms on boron-doped graphite were estimated to be lower than pristine graphite even at temperatures of 673 K. The adsorption energies of the gases prevalent at the anode side of the fuel cell such as CO and H2 was studied on pristine and boron-doped carbon supported Pt systems in addition to the CO and H2 oxidation kinetics. The activation barriers for these reactions were calculated.