Supported Platinum electrocatalysts are used in Polymer electrolyte membrane fuel cells (PEMFC) to catalyze the hydrogen oxidation and oxygen reduction reactions. The high surface to volume ratios of supported catalysts maximizes the area of catalytic surfaces available for reactions. A proper distribution of platinum nanoparticles on the carbon support minimizes the loss in activity due to agglomeration of the nanoparticles. Since colloidal interaction forces drive the deposition process, it is imperative to understand the interactions between the support and the catalyst nanoparticles. This interaction is used as the basis of our modeling of electrode structure using a hierarchical scheme of successively more complex structures. The free energy of interaction we measure is scaled by the Hamaker coefficients for the materials. We estimate these coefficients from optical spectra using Lifshitz theory; optical spectra for the carbon support and catalyst particles are measured. The Hamaker coefficients we compute are used in computer simulations of the formation of particle ensembles using a stochastic model reported earlier that takes into account near neighbor interactions. The sensitivity to the values of the Hamaker coefficient on the processes of nanoparticle aggregation, dispersion on the surface and loading of catalysts will be discussed. Kinetic Monte Carlo calculations are performed to obtain nanoparticle cluster structure with and without the effect of the support interaction. We will discuss the implications of the strength of the various interactions on the expected durability of fuel cell electrocatalyst structures.