Nano-Scale Simulation of Platinum Particle Dissolution, Re-Deposition, and Transport

Abstract

Dissolution and redeposition of platinum (Pt) in the catalyst layer of polymer electrolyte fuel cells (PEFCs) results in a loss of electrochemically active surface area and increases in the overpotential for the oxygen reduction reaction, reducing efficiency.1 Typically, carbon supported Pt (Pt/C) catalyst exhibits Pt particles both on the external surface of the carbon support as well as within the internal micro-pores and smaller mesopores of the support that are known to be inaccessible to ionomer. Experimental evidence suggests that there may be preferential exchange of Pt between external and internal Pt.2,3Here, we apply a computational model of the ionomer coated catalyst surface in combination with a Pt particle embedded within a water-filled micro-pore. To evaluate the transfer of Pt between internal and external Pt, we have developed a three-dimensional computational model to simulate proton and Pt ion transport using a Poisson-Nernst-Planck model in combination with Pt dissolution and redeposition as well as Pt oxide coverage models (Figure 1a). Our results suggest that the external Pt particle in contact with the incomer increases in a diameter, whereas the Pt particle in the pore reduces its diameter. The Figure 1 c) shows the change of the diameter of the external and internal particles with the electrode potential cycling. This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271. Figure 1