Catalysts for the Oxygen Reduction Reaction

The fundamental reaction occurring inside a fuel cell is the oxygen reduction reaction (ORR), where oxygen and hydrogen are forming water. The critical challenge for improving fuel cells is making an advancement in the catalyst for ORR. While there have been many various approaches, we have shown that by using a dealloyed composite of platinum and nickel, nano-sized pores are left that can be filled with an ionic liquid, greatly increasing the catalytic efficiency.

A platinum-nickel alloy has been shown to be one of the best catalysts for ORR. Dealloying removes the majority of the nickel leaving behind many small pores while greatly increasing the surface area, another important factor in catalysis. Also, there is a very active platinum rich outer surface, while most of the less catalytically reactive nickel remains on the inside.

To make the system an even better catalyst, an ionic liquid is added to the pores. An ionic liquid (IL) can be electrically conductive, meaning the electrons and protons necessary for ORR are able to travel through the IL to the platinum-nickel catalyst surface and back. In addition, an IL with high oxygen solubility was chosen, which means we are not limited by the amount of oxygen we can get to react. Combining these components, we have a very reactive surface catalyst, with a greater area from dealloying, as well as a higher oxygen solubility, all of which make a better, more efficient catalyst for ORR and fuel cells.