In the search for sustainable fuels, hydrogen remains of interest for long-range vehicular applications. There are numerous technical challenges that must be overcome in order to achieve significant market penetration. The durability of PEM fuel cells remains one of the most significant barriers for the commercialization of PEM fuel cells. Among various failure modes that shorten the lifetime of the PEM fuel cells, the degradation of carbon support Pt catalyst (Pt/C) due to carbon support corrosion is one of the most important factors . Carbon is known to undergo electrochemical oxidation to surface oxides during fuel cell operation time. The presence of oxygen-containing groups can weaken the interaction between the carbon support and the catalytic nanoparticles, causing sintering of platinum nanoparticles and thus influence the conductivity of electrons and protons in the fuel cell and affect the lifetime of the fuel cell .
In the work described here, molecular dynamic simulations are performed to calculate the adhesion energy and force of platinum nanoparticles on carbon surfaces. To investigate how the carbon corrosion will affect the adhesion, we use three types of carbons surfaces: epoxy oxidized carbon surface, hydroxyl oxidized carbon surface and perfect carbon surface. Different shapes and sizes of nanoparticles (Pt) are applied to study their shape and size effects on the adhesion energy. Oxidized carbon surface of different oxidation rate are used to study the oxidation effect on adhesion energy. To mimic the real catalyst layer environment, water and Nafion are added as essential components. Simulation results are then compared with experimental results measured by nano-scale force sensitive manipulators, which are placed inside a SEM and operated while imaging the area of interest. Nano manipulators can be used to measure the adhesion of the catalyst particles to the substrate by determining the force required to dislodge them. Adhesion force between different types and sizes of platinum and three different carbon surfaces with varying oxidation ratios are explored to better understand the mechanism of how will carbon corrosion affect the fuel cell durability.
This work was supported by the STAIR program at the University of Tennessee, funded by NSF under agreement number: DGE 0801470.
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