The Oxygen Reduction Activity of the Pt-Based Catalyst: First Principles Study
|Course||Condensed Matter Physics|
|Keywords||O2 adsorption diffusion dissociation DFT stability|
The extensive application of fuel cells will result in a new generation green power source revolution. Among the fuel cells, the Proton Exchange Membrane Full cell （PEMFC） is the one with very high prospective. The electrode catalyst of the conventional commercial PEMFC is the Pt/C, a catalyst with Pt nanoparticles deposited on carbon. The oxygen reduction reaction （ORR） is the key reaction that impacts the PEMFC performance, in which the dissociation of oxygen is the rate determine step. The ab initio simulation calculations based on the density functional theory （DFT） can help to investigate the catalytic reaction mechanism and explain the experimental phenomena. However, many calculation results are still inconsistent with experiments, and there still exist some experimental observations that are not well explained by the simulation calculations.In this article, we use first priciple calculation method to investigate the adsorption, difffuison and dissociation of O2 on the pure Pt（111） and the Pt3Ni alloy （111） surface. In addition, we also investigate the adsorption and diffusion of Pt on the NbO2（110） surface.The meaningful results gained as follows:1. The t-h-b adsorption configuration of O2 transform to t-h-b adorption easily, which explain the reason why no t-h-b configuration can’t be observed in experiments. We get the O2 dissociation process and identify the dependence relationship of dissociation energy barrier with O2 coverage.2. Pt3Ni（111） surface can weaken the poison of O and OH species to catalyst so as to enhance the oxygen reduction reaction catalystic activity. The dissociation energy barrier is so high that the directly dissociate of O2 is impossible occur. At least for Pt base alloy catalyst, the first elementary reaction is not dissociation of O2 but to form OOH species.3. With NbO2 support Pt can enhance the oxygen reduction reaction is also due to weakening the poison of O and OH species to catalyst. Pt can be anchored strongly at NbO2（110） surface which increase the chemical stability against Pt dissolution. Our study results explain the experiments phenomenons reasonably, which has strong instructly meaning for the prepareation of new catalyst.