Catalyst inks and method of application for direct methanol fuel cells
Assignee:
The Regents Of The University Of California
Inventors:
Piotr Zelenay, John Davey, Xiaoming Ren, Shimshon Gottesfeld, Sharon C. Thomas
Patent:
Ultrasonic Nozzle used in Membrane Electrode Assembly (MEA)
During ultrasonic spraying, agglomerated particles/constituents of a fluid are broken up and very small droplets are produced (median size range typically 20-70 μm). This results in a very fine spray with small uniform particles. Depending on the nature of the liquid being sprayed and the desired drop size, the flow rate of the spray can be as little as a few μL per second. Drop size is governed by the frequency at which the ultrasonic spray nozzle vibrates, allowing the user to select a drop size range for their needs.
The ultrasonic spray system for membrane electrode assembly (MEA) fabrication incorporates a 60-kHz ultrasonic spray nozzle with broadband ultrasonic generator, a gas pressurized reservoir or low-flow peristaltic pump ink delivery system, a gas shroud around the spray nozzle for directing the spray onto the substrate, and a movable, heated vacuum table, which holds the ionomeric membrane to be sprayed.
During spraying, the reservoir holding the ink is continuously sonicated (10-20% on-time duty cycle) by a ½ inch diameter ultrasonic probe and cooled in an ice bath. Sonication prevents the ink from segregating and catalyst particles from agglomerating.
