Scientists Invent Hydrogen-Sucking Sponge For Fuel Cell EVs

Hydrogen fuel cell electric vehicles have a little catching up to do compared to their battery-powered cousins. But improvements in the technology are coming thick and fast. The latest development arrives via Sandia National Laboratories, and it involves a spongy new material with "unusual and unexpected" properties.

So, why do hydrogen fuel cell EVs need a sponge?

Tackling the hydrogen storage problem

"Improvements in the technology" is a shorthand way of saying that fuel cell EVs need to come down in price before they appeal to the mass market.

For now, battery EVs are winning hearts and minds, at least when it comes to passenger cars. They're already closing in on the cost of a typical gas-powered vehicle, and the EV charging station network is growing rapidly.

Part of the affordability problem for fuel cell EVs has more to do with the fuel than the car itself. Hydrogen is an abundant fuel, but it is not particularly energy-dense. The current approach is to compress hydrogen gas for use onboard a moving vehicle, but that runs into cost issues.

The emerging solution is to trap hydrogen in a sponge-like, solid mass. Ideally, such a system would be able to store more hydrogen at a lower cost.

The sponge field is still in its early stages, said Sandia chemist Vitalie Stavila:

"There are two critical problems with existing sponges for hydrogen storage," Stavilla explained. "Most can't soak up enough hydrogen for cars. Also, the sponges don't release and absorb hydrogen fast enough, especially compared to the five minutes needed for fueling."

If you caught that thing about five-minute refueling, you're on to something. Battery EVs take a long time to charge. That's an inconvenience that inhibits mass adoption.

Fuel cell EVs only take a few minutes to charge, much like filling up a gas tank. So for zero-emission technology to replace gasoline on a massive scale, the ideal substitute would be an EV that can refuel as quickly as filling a conventional car -- and that is priced in a similar range, too.

A better sponge for fuel cell electric vehicles

That's where the new research comes in.

The study is a collaboration between Sandia, Lawrence Livermore National Laboratory, and the National Institute of Standards and Technology in the U.S., in partnership with graduate student Natchapol "Golf" Poonyayant of Thailand's Mahidol University.

Poonyayant inspired the research with his idea for leveraging nanotechnology to develop a more efficient material for hydrogen storage.

Working at the far end of the nanoscale, Poonyayant and the team developed a way to insert metals and nitrogen into particles of carbon.

The results were published in the journal Advanced Materials Interfaces under the title, "Hydrogen Storage: Nanointerface-Driven Reversible Hydrogen Storage in the Nanoconfined Li–N–H System."

The team developed tiny particles of carbon riddled with miniature pockets, which hold particles of the compound lithium nitride. Previous research shows that lithium nitride acts like a chemical "sponge" to absorb and release hydrogen. The challenge is to develop an efficient platform for managing the reaction between the two, and it looks like carbon fits the bill.

The new nanoscale material exhibits four "unusual and unexpected" characteristics that indicate a way forward, the researchers said.

Most significantly, the modified particles of carbon release hydrogen in only one step, which compares favorably to the two-step process required in a bulk material.

That leads to a second advantage. The new material also releases hydrogen more quickly than bulk material.

An important third advantage is that the new material absorbs hydrogen more rapidly, indicating the potential for rapid refueling.

Finally, the new material compares favorably to other similarly engineered materials because the "host" material -- the carbon -- can accommodate a fairly high percentage of introduced materials. The amount of lithium nitride in the carbon particles clocks in at approximately 40 percent.

So, why is it better?

One important next step is to define exactly why the new material behaves so well.

Research team members from the Livermore lab were able to determine that the nanoscale size of the lithium nitride particles -- they are only three nanometers wide -- practically eliminates inefficient, intermediate steps in the chemical reaction when absorbing and discharging hydrogen:

"Taking the path of least resistance, the material undergoes a single-step path to full hydrogenation. Similarly, once hydrogenated, the nanoparticles release hydrogen by the lowest energy pathway available, which in this case is direct hydrogen release back to lithium nitride."

The next part of the task is to achieve a more precise understanding of the mechanism at work.

The team will also work on ratcheting down the amount of carbon needed.

If this all sounds like it will take a long time, it might.

Meanwhile, even if fuel cell EVs have yet to make a mark on the passenger car market, they are beginning to emerge in other important sectors including logistics (forklifts and other work vehicles), railroads, and long-distance freight hauling.

The U.S. military is also emerging as an important market for fuel cell vehicles.

Readers please note: The research team has dedicated their work and the resulting study to Natchapol "Golf" Poonyayant, who met an untimely death at age 25 while the study was still in the writing process.

Image (cropped) via Sandia National Laboratories.