Discovering and Leveraging Catalytic Possibilities Offered by Superprotonic Electrolytes

About This Grant

This project will enable high efficiency conversion of fuels to electricity using a conversion device called a fuel cell. The key components of the fuel cell are the proton conducting electrolyte and the catalysts that facilitate the reaction of oxygen with protons to generate electricity. The project will create advanced electrocatalysts that operate at ~500 degrees Fahrenheit. This temperature is hot enough to accelerate the desired fuel conversion reaction, yet cool enough to slow unwanted material degradation. The research team has previously identified catalyst materials with high activity, but they degrade because they react with the electrolyte in the fuel cell. To address this challenge, the team will utilize ultra-thin barrier layers that are permeable to protons but block the reaction of the catalyst material with the electrolyte. In parallel, they will utilize advanced characterization techniques to reveal the pathway for the reaction of oxygen with protons. This will allow rational design and selection of high activity catalysts. The project will include researchers at various academic levels, and it will support training through internships for high school and undergraduate students, as well as postdoctoral research opportunities for early career professionals. This research aims to design oxygen reduction catalysts suitable for use in solid acid fuel cells. These fuel cells operate at ~ 250 degrees C and incorporate a superprotonic solid acid, cesium dihydrogen phosphate (CsH2PO4) with a proton conductivity of ~ 10-2 S/cm, as the electrolyte. Despite operating at temperatures higher than polymer electrolyte membrane fuel cells, oxygen reduction rates on the Pt catalysts of solid acid fuel cells are relatively low, necessitating the development of alternative catalyst materials. Possible candidates, including Pd and Ag, which show evidence of higher activity than Pt, react with the electrolyte and their activity quickly degrades. The PI proposes multi-layered structures in which proton-permeable barrier layers prevent these detrimental interactions. These structures and the reaction pathways facilitating oxygen reduction will be studied using a suite of tools including X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and mass spectroscopy of evolved gases, in addition to electrochemical characterization by voltammetry and impedance spectroscopy. These studies are aimed at uncovering the reason for the poor activity of Pt in solid acid fuel cells and enabling rational design and selection of high activity alternatives. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.