Schematic and implementation of encapsulated nanoporous nanoparticle catalysts for high-performance PEMFC oxygen reduction.

Schematic and implementation of encapsulated nanoporous nanoparticle catalysts for high-performance PEMFC oxygen reduction.

We have developed the most active discovered fuel cell catalysts for automotive applications. The catalysts are based on nanoporous nanoparticles and are developed using electrochemical dealloying. In a nanoporous nanoparticle, one component is dissolved away leaving behind the other material in a porous matrix. The pore size of these nanoparticles is between 3-4 nanometers (6-10 atoms). The pores are filled with an ionic liquid; the one used in this research soaks up oxygen and repels water. The ionic liquid takes oxygen and turns it into water, making the process more effective. These fuel cell catalysts have been made in a lab, and real fuel cells have been made from them showing all the performance increases seen in the lab. The goal is to bring these techniques to an industrial scale in order to develop fuel cell technology for automotive applications.

Recent advances in oxygen reduction reaction catalysis for proton exchange membrane fuel cells (PEMFCs) include i) the use of electrochemical dealloying to produce high surface area and sometimes nanoporous catalysts with a Pt-enriched outer surface, and ii) the observation that oxygen reduction in nanoporous materials can be potentially enhanced by confinement effects, particularly if the chemical environment within the pores can bias the reaction toward completion. Here, these advances are combined by incorporating a hydrophobic, protic ionic liquid, [MTBD][beti], into the pores of high surface-area NiPt alloy nanoporous nanoparticles (np-NiPt/C + [MTBD][beti]). The high O2 solubility of the [MTBD][beti], in conjunction with the confined environment within the pores bias reactant O2 toward the catalytic surface, consistent with an increased residence time and enhanced attempt frequencies, resulting in improved reaction kinetics. Half-cell measurements show the np-NiPt/C+[MTBD][beti] encapsulated catalyst to be nearly an order of magnitude more active than commercial Pt/C, a result that is directly translated into operational PEMFCs.

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