IEEE SpectrumIron-Platinum Catalyst Keeps Fuel Cells Clean, Even in Cold We...

A novel catalyst protects fuel cells from contaminants, and could help China catch up in battery-free EVs

This bus in Zhengzhou, a city in central China's Henan province, is powered by hydrogen fuel cells./Photo: Imaginechina/AP

Batteries are currently outpacing fuel cells in the technological race to power the electric vehicle. Lithium batteries keep getting cheaper, while fuel cells remain hampered by pricey, short-lived platinum catalysts. An advance reported today in Nature by researchers in China suggests that adding a bit more platinum—albeit in a novel form—could help fuel cell cars catch up.

The report from a group at theUniversity of Science and Technology of China(USTC), in Hefei, also shows that China is catching up to fuel cell leaders such as Japan and Korea. China’s automakers already make the majority of the world’s battery electrics, and the government is keen to see them dominate in fuel cells, too. Last year Beijing and local governments provided US $12.4 billion in subsidies for fuel cell vehicles, according to the Financial Times.

Platinum catalysts drive the core reaction inside proton-exchange membrane fuel cells (the kind used in cars) that sustains their electric circuit—the same reaction that creates the water that dribbles out of vehicle tailpipes. Junling Lu, a professor with USTC’s Hefei National Laboratory for Physical Sciences at the Microscale, says they have found a way to protect those platinum catalysts from a ubiquitous contaminant: carbon monoxide. It tightly binds to platinum, blocking the catalytic action.

The carbon monoxide is present because most hydrogen fuel is produced from hydrocarbon fuels. Even after costly purification, hydrogen fuel contains up to 0.2 parts per million carbon monoxide (CO). Over time, it builds up on the catalyst, slowing the fuel cell reaction, and such ‘poisoning’ snowballs each time a fuel cell vehicle starts up in cold weather. “Even the highest grade hydrogen has trace amounts of CO that can eventually deactivate the fuel cell electrodes,” says Lu.

Lu and his colleagues found a solution by designing a novel catalyst—platinum particles peppered with iron oxide—that can rapidly burn away CO in hydrogen. The catalyst selectively converts CO to harmless CO2and, critically, it works across a broad temperature range. Their testing confirmed a 200-fold reduction in CO between -75 and 107 degrees C, which he says is a huge improvement over previous CO-selective catalysts. “All the catalysts in the literature were only operating above room temperature,” says Lu.

In the near term, Lu imagines their catalysts extending the operating life of fuel cell vehicles’ costly stacks. Down the road, he says onboard fuel clean-up could allow the use of lower-grade hydrogen fuel with a lower price that “all of the people can bear.”

“They may have a good solution here. It looks like it could work,” saysWilliam Goddard, director of the California Institute of Technology’s Materials and Process Simulation Center and a designer of fuel cell catalysts who was not involved in today’s advance.

That said, Goddard notes that the CO problem should eventually go away as hydrogen production shifts from stripping fossil fuels to applying electrolysis to water using renewable or nuclear energy. He adds that what’s really needed to make fuel cell vehicles competitive are cheaper catalysts within the fuel cell stack. The platinum-rich stack contributes to the hefty $85,000 price tag on Toyota Motor’s Mirai fuel cell sedan.

China’s government seems to expect that goal to be reached sometime within the coming decade. By 2030, its plans call for 1 million fuel cell vehicles to be cruising China’s roads. To get there, it is financing domestic research such as USTC’s and also providing rich subsidies to spur development by Chinese companies—up to $30,000 per vehicle plus additional local subsidies according to theFinancial Timesreport.

Over the past two years, several Chinese firms have bought stakes in foreign fuel cell firms and set up joint ventures to access advanced technology. Most recently, in November 2018, Chinese engine and auto parts manufacturer Weichai Power acquired 20 percent of Canadian fuel cell pioneer Ballard Power Systems. In a separate deal it acquired a 20 percent stake in U.K.-based fuel cell maker Ceres Power.

IEEE Spectrum, 2019-1-31

https://spectrum.ieee.org/energywise/green-tech/fuel-cells/chinese-catalyst-keeps-fuel-cells-clean