Researchers develop optimized electrospray technique for ultra-low platinum loading in fuel cells with high performance
|The electrospray (top) and the deposited nanostructure (bottom). Source: UNED. Click to enlarge.|
A group of researchers from UNED (National Distance Education University) in Spain reports developing an optimized electrospray method for manufacturing the membrane electrode assembly (MEA) in PEM fuel cells with ultra-low platinum loadings that exceed US Department of Energy (DOE) targets.
Optimization of the control parameters result in electrosprayed layers with nanostructured fractal morphologies with dendrites formed by clusters (about 100 nm diameter) of a few single catalyst particles rendering a large exposure surface of the catalyst.
With ultra-low platinum loadings of 0.01 mg/cm2 in both electrodes, the platinum utilization was so high that PEM fuel cells delivered power reaching up to 10 kW per gram of platinum. The DOE target for the period 2017-20 is 8 kW per gram of platinum with a loading ten times higher. A fuel cell with the MEA developed by these researchers has been operating for more than 1,000 hours without interruption.
The electrospray technique, which has been patented, copes with any fuel cell size from laboratory to marketable dimensions and could be used for low-cost industrial production, the researchers said.
The method deposits thin nanostructured layers of electrocatalyst particles on the fuel cell electrodes, which are joined by simple contact on both sides of the polymeric membrane, making the MEA.
The methodology used for the deposition of the catalytic layer (electrospraying) is the key to increase the performance.
We were able to control the morphological properties (porosity and roughness) of the material generated by the catalyst particles when deposited, substantially increasing the active surface. As the performance depends on the surface of the catalyst particles exposed to the reactive gas, and it was made very large, we have reached a high performance.—Jose Luis Castillo, professor in the Department of Mathematical Physics and Fluids
The cost of the platinum catalyst is about the 30% of the total price of a fuel cell; hence, the ability to build fuel cells at competitive prices is one of the challenges being pursued by the research community.
In addition to potential use by the automotive industry, lower-cost and better-performing fuel cells could also be used to address the problem of discontinuity in renewable electricity generation by using excess renewable electricity to generate hydrogen for later conversion via fuel cells.
S. Martin, P.L. Garcia-Ybarra, J.L. Castillo (2010) “High platinum utilization in ultra-low Pt loaded PEM fuel cell cathodes prepared by electrospraying”, International Journal of Hydrogen Energy 35 10446-10451 doi: 10.1016/j.ijhydene.2010.07.069