Scavenger Nanoparticles Pave Way for EV Fuel Cells

Researchers have long investigated fuel cells as alternatives to the lithium batteries used in electric vehicles (EVs) to provide a cleaner source of energy with a longer driving range. However, so far they have yet to find a suitable, practical, and cost-effective catalyst for these devices to make that vision a reality.

Now engineers at the University of Illinois Chicago (UIC) may have a solution to this problem with the development of a material that can produce durable fuel-cell systems at a cost-competitive price to current lithium batteries used in EVs, they said.

The team, led by Reza Shahbazian-Yassar, professor of mechanical and industrial engineering at the university’s College of Engineering, discovered a material to add to the device catalyst that can produce an inexpensive and durable iron-nitrogen-carbon fuel cell.

The material — an additive comprised of tantalum-titanium oxide nanoparticles--acts as a “scavenger” can find and deactivate free radicals, or unstable particles like atoms, molecules, or ions called free radicals and hydrogen peroxide, that destabilize the fuel cell, researchers said.

The Promise of Fuel Cells

The findings bring scientists “much closer to making fuel cell-powered vehicles and other fuel cell technologies a reality,” Shahbazian-Yassar said in a press statement.

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Indeed, fuel cells are an attractive alternative to batteries because of their higher driving range, fast recharging capabilities, lighter weight, and smaller volume. The technology relies on catalyst-driven chemical reactions to create energy, taking advantage of abundant elements such as oxygen and hydrogen.

Moreover, while lithium batteries can typically achieve a range of 100–300 miles on one charge, fuel cells can achieve more than 400 miles on a single charge — which can be done in under five minutes. Unfortunately, the catalysts used to power their reactions are made of materials that are either too expensive (i.e., platinum) or too quickly degraded to be practical. 

Unfortunately, traditionally it’s been difficult to find economical ways to separate and store hydrogen, with the catalysts used to power their reactions comprised of materials that are either too expensive (i.e., platinum) or too quickly degraded to be practical, researchers said. 

Investigation & Results

To find the scavenger particle, the team turned to electron microscopy to capture highly detailed, atomic-resolution images of the materials under a variety of service conditions, Shahbazian-Yassar explained. The high-resolution imaging of the atomic structures allowed the team to define the structural parameters needed for the additive to work, he said.

“Through our structural investigations, we learned what was happening in the atomic structure of additives and were able to identify the size and dimensions of the scavenger nanoparticles, the ratio of tantalum and titanium oxide,” Shahbazian-Yassar explained in a press statement. “This led to an understanding of the correct state of the solid solution alloy required for the additive to protect the fuel cell against corrosion and degradation.”  

Ultimately, researchers discovered that the best option for this protection is a solid solution of tantalum and titanium oxide with nanoparticles that are about five nanometers in size, they said. The experiments also revealed that the solution also requires a 6:4 ratio of tantalum to titanium oxide.

“The ratio is the key to the radical scavenging properties of the nanoparticle material and the solid-state solution helped sustain the structure of the environment,” Shahbazian-Yassar explained in a press statement. 

Researchers published a paper on their work in the journal Nature Energy.

Once they solidified the parameters for the scavenger-nanoparticles material, researchers added it to the reactions of fuel-cell systems. The result was that the use of the particle suppressed the hydrogen peroxide yield to less than 2 percent--a 51 percent reduction from previous catalysts used without the material, they said.

Moreover, the  current density decay of the fuel cells using the additive material in its catalyst was reduced from 33 percent to only 3 percent, researchers added.