The Long View -- This graphic summarizes a possible future, where fossil fuels (on the right) feed various applications of hydrogen fuel cells while renewable energy sources (on the left) power battery-electrics.
Mindy Zhang says the day Toyota’s Mirai hydrogen fuel cell sedan went on sale in California in 2015 was “a major milestone for the R&D community.”
But the group manager of Material Research at the Toyota Research Institute, North America (TRI-NA) also knows it was just one step on a path that extends well into the future.
“Toyota envisions a ‘hydrogen society’ that will replace the existing fossil fuel-based energy systems,” says Zhang. “We believe fuel cells will play a key role in this. But we have a lot of work to do before that can happen.”
Zhang’s specific piece in this complex puzzle is the development of catalytic materials for the next generation of fuel cells. In 2015, the catalyst research team in Ann Arbor, Michigan expanded its efforts on fuel cell materials to include in-house laboratory experiments with additional staff members.
Company-wide, the mission is to expand the limits of fuel cell technology until it performs on par with Toyota’s current hybrid systems. That will require significant increases of fuel efficiency, driving range and production volume while reducing the cost.
“It’s going to be very hard,” says Zhang. “Some of it can be achieved through continuous improvement. But we will also need breakthroughs in the technology.”
In simple terms, a fuel cell combines oxygen in the air with hydrogen stored in the vehicle’s fuel tank to create water vapor (aka H2
0). Electrons (aka electricity) are released in the process.
There are different ways to go about this. Toyota’s fuel cell system employs a polymer exchange membrane-based electrode assembly (MEA). Modify the MEA and you affect its efficiency.
Zhang says TRI-NA is exploring such modifications on three key fronts:
The team is experimenting with the shape and configuration of nanocrystals on the surface of the membrane to increase its surface area and activity. That, in turn, can increase the system’s power density, a key to making the system lighter, more compact and less expensive.
Zhang says the shape-controlled nanocrystals that could deliver the desired power density have been identified. But, thus far, they have only been produced in very small quantities in a laboratory. The challenge is to scale them up to real-world production levels. Questions about durability will also need to be answered.
Ionic liquids —
The chemical reaction in a fuel cell occurs at the interface between its electrode catalyst and the polymeric electrolyte. As such, the team is testing different ionic liquids in search of the one that maximizes the reaction rates. Zhang says significant improvements have been achieved in the lab, but need to be validated at scale. If successful, the new technology will be handed over to Toyota Motor Corporation for use in the company’s third generation fuel cell system later this year.
Heat management —
The Mirai’s ample grille isn’t just a fashion statement; it’s a necessity to accommodate the oversized radiator required to manage the heat generated by its fuel cell stack. Zhang says the team is trying to find ways to modify the system to mitigate the cooling challenge. One in-house research effort involves a new design of two-phase cooling that leverages phase changes (evaporation/condensation) to enhance the heat exchange rate. That will give future vehicle designers more flexibility and could lead to parts sharing with hybrid vehicles, helping to lower costs.
Rather than go it alone on this one, TRINA is collaborating with the Los Alamos National Laboratory in New Mexico. The proof-of-concept phase — during which the two teams will each come up with a different solution — is expected to be completed by this time next year.
“This is a long journey,” says Zhang. “Think about how long it took to develop hybrids into a mainstream technology. Fuel cell is a bigger challenge. But, as a company, we are working very hard to make it better. I’m confident we will get there.”
By Dan Miller