Imagine that you can drive a fuel cell electric car that does not need to be recharged and can be refueled as your gasoline/diesel cars without any carbon emission. Moreover, with the fuel cell car, you can get rid of the "EV Range Anxiety" and the "fear of winter," two major roadblocks to the massive market penetration of the battery-electric car.
That's possible with the replacement of the expensive platinum group metal (PGM) catalysts in the fuel cell with the low-cost PGM-free Fe-N-C catalysts, says Jian Xie, an Indiana University-Purdue University Indianapolis, professor of mechanical and energy engineering and a research member of the IUPUI Integrated Nanosystems Development Institute and the Richard G Lugar Center for Renewable Energy.
In a paper recently published in Nature Energy, Xie and a team of authors -- including School of Engineering and Technology Ph.D. student Chenzhao Li (the first author) -- detail how they have solved a decades-old problem with the novel PGM-free Fe-N-C catalyst in the fuel cells.
For the polymer electrolyte membrane fuel cell (PEMFC) manufacturers, how to replace the expensive PGM catalysts with PGM-free catalysts has proved frustratingly elusive. Such a PGM-free catalyst would make PGMFC 10 times cheaper than those currently used in several applications such as cars, trucks, boats, and locomotives.
The fault lies in the expensive PGM catalysts.
The sluggish oxygen reduction reaction (ORR) needs to use the expensive platinum-based catalysts to accelerate, making the fuel cell work with the performance of a gasoline/diesel engine. Unfortunately, platinum is costly with minimal reserve on the earth.
Engineers and scientists have tried to replace the PGM catalysts with PGM-free catalysts, but they encounter two challenges: low activity and stability, as the activity and stability of PGM-free catalysts usually are one or two orders of magnitude lower than their PGM counterparts. Xie and his team synthesized an iron-nitrogen-carbon catalyst with an atomically fine dispersion of catalytically active sites. These catalysts demonstrated the remarkable performance of which the activity matches that of the highly active platinum catalyst. At the same time, the stability is on the same order of magnitude as the platinum catalyst using the after post-chemical vapor deposition treatment, and the catalyst showed more impressive stability than the platinum catalyst.
This publication is the fruit of the "Mesoporous Carbon Based PGM-Free Catalyst Cathodes" (a project sponsored by the Department of Energy, Hydrogen and Fuel Cell Technology Office of the Energy Efficiency and Renewable Energy Office.) Xie and Chenzhao Li, a doctoral student as well as other Ph.D. students and postdocs in this team, have designed the high-performance membrane-electrode assemblies with a novel catalyst-coated membrane method which is rarely applied to PGM-free catalyst and examined the catalyst's performance when subjected to the rigorous stresses encountered in real-life use. As a result, the catalysts developed exceeded the Department of Energy 2025 performance target for PGM-free catalysts for the first time ever, exhibiting the world record activity of all iron-based PGM-free catalysts.
Informed by the detailed atomic-level physical characterization and supercomputer simulations of the active site difference, the team plans to further balance/tune the activity and stability of this catalyst to rival and possibly surpass platinum in the near future.
