Mechanisms and Rates for Improved Fuel Cell Cathode Catalysts and Supports from First Principles Based Methods

California Institute Of Technology, Pasadena CA

Investigators

Abstract

If progress is to be made at ultimately overcoming the technical and cost limitations of PEM fuel cells, a significant investment in the fundamental science of the reactions taking place must be made. The objective for this proposal is to determine the detailed atomistic mechanism including free energy barriers for the oxygen reduction reaction at PEM fuel cell cathodes. The focus is on how the mechanism and rates depend on alloy composition, distribution between surface and bulk regions, and solvent. The computational results would be tested by predicting how binary and ternary catalysts would be expected to improve selectivity, rates, and lifetime. In addition, the PIs, William A. Goddard III Boris Merinov, both of the Materials and Process Simulation Center at California Institute of Technology, propose to determine mechanisms of catalyst degradation and how they depend on alloy composition. The result is to be a computational model sufficiently accurate to be useful in guiding both experiments and engineering applications. There has previously been no practical means to couple such a wide range of reactive phenomena based solely on first principles. This novel approach would predict data for engineering models from first principles, allowing new systems to be designed computationally and then tested against experiment. To enable this model testing, collaborations have been arranged with Argonne National Labs and with Ford Scientific Labs to carry out experiments on those alloys predicted to be most promising. This model should aid the development of accurate engineering models informed from the theory and simulations but adjusted to incorporate results from experiments. This approach will be essential to develop the improved materials and processes needed to enable new alloys to meet the current targets for improved fuel cells. The development of improved catalysts (more efficient, longer-lived) should accelerate development of efficient fuel cells that would be commercially viable for transportation, energy production and storage, with the resultant environmental impact. In the broader sense, in addition to contributing significantly to the development of improved alloy catalysts for fuel cell cathodes, the successful coupling of computational tools including QM through ReaxFF reactive dynamics to simulation of the catalyst/support system would apply to other problems in catalysts, materials, and energy.