Researchers led by a team at Washington State University (WSU) have developed a unique and inexpensive nanoparticle catalyst that allows a solid-oxide fuel cell to convert logistic liquid fuels such as gasoline to electricity without stalling out during the electrochemical process. The research, featured in the journal Applied Catalysis B: Environmental, could result in highly efficient gasoline-powered cars that produce low carbon dioxide emissions that contribute to global warming.

In addition to WSU, the team included researchers from the University of Massachusetts, Lowell; Stony Brook University; Brookhaven National Laboratory; Foshan University in China; and Pacific Northwest National Laboratory.

Fuel cells offer a clean and highly efficient way to convert the chemical energy in fuels directly into electrical energy. They are similar to batteries in that they have an anode, cathode and electrolyte. However, unlike batteries which only deliver electricity they have previously stored, fuel cells can deliver a continuous flow of electricity as long as they have fuel.

Because they run on electrochemical reactions instead of making a piston do mechanical work, fuel cells can be more efficient than the combustion engines in cars. When hydrogen is used as fuel, their only waste product is water.

Despite the great promise of hydrogen fuel cell technology, however, storing high-pressure hydrogen gas in fuel tanks creates significant economic and safety challenges. There is little hydrogen gas infrastructure in the US, and the technology’s market penetration is very low.

We don’t have readily available fuel cells that can run on a logistic liquid fuel such as gasoline.

—Qusay Bkour, lead author

Unlike pure hydrogen fuel cells, the developed SOFC technology can run on a wide variety of liquid fuels, such as gasoline, diesel, or even bio-based diesel fuels, and doesn’t require the use of expensive metals in their catalysts. Cars powered by gasoline SOFCs could use existing gas stations.

Fuel cells that run on gasoline, however, tend to build up carbon within the cell, stopping the conversion reaction. Other chemicals that are common in liquid fuels, such as sulfur, also stop the reactions and deactivate the fuel cell.

The carbon-induced catalyst deactivation is one of the main problems associated with the catalytic reforming of liquid hydrocarbons.

—Qusay Bkour

Bkour et al.

For their SOFC fuel cell, the WSU team used an inexpensive catalyst made from nickel and then added nanoparticles of the element, molybdenum.

We find that a Ni-Mo/YSZ catalyst displays a high reforming activity and stability with an isooctane conversion of 90% and H₂ yield of 76% with less degree of coking and sintering as compared to a Ni/YSZ catalyst. Our XRD results indicate that a Ni-Mo solid solution is formed. Raman results also suggest that the presence of well dispersed Mo=O species over a Ni surface can be a possible active site that is related to the high coke resistance of Ni-Mo/YSZ catalysts.

DFT-based calculations indicate that Ni-Mo/YSZ catalysts enhance the carbon-tolerance by increasing activation barriers for the C–H bond cleavage and C–C coupling as compared with the Ni/YSZ system. A Ni-Mo catalyst is used as an internal micro-reforming layer on top of conventional Ni-YSZ anode-supported single cells. The single cell displays a significantly improved stability with a low degradation rate.

—Bkour et al.

Testing their molybdenum-doped catalyst, their fuel cell was able to run for 24 hours straight without failing. The system was resistant to carbon build-up and sulfur poisoning. In contrast, a plain nickel-based catalyst failed in an hour.

The work was funded by the Office of Naval Research and Washington’s Joint Center for Deployment and Research in Earth Abundant Materials (JCDREAM).

Resources

• Qusay Bkour, Fanglin Che, Kyung-Min Lee, Chen Zhou, Nusnin Akter, Jorge Anibal Boscoboinik, Kai Zhao, Jake T. Gray, Steven R. Saunders, M. Grant Norton, Jean-Sabin McEwen, Taejin Kim, Su Ha (2020) “Enhancing the partial oxidation of gasoline with Mo-doped Ni catalysts for SOFC applications: An integrated experimental and DFT study,” Applied Catalysis B: Environmental, Volume 266, 118626 doi: 10.1016/j.apcatb.2020.118626