Research pushes auto industry closer to clean cars powered by direct ethanol fuel cells

Zhenxing Feng from Oregon State University College of Engineering helped lead the development of a catalyst that solves three problems associated with direct-ethanol fuel cells (DEFC): low efficiency, the cost of catalytic materials and the toxicity of chemical reactions inside the cells.  

With collaborators from Oregon State, the University of Central Florida and the University of Pittsburgh, results showed putting fluorine atoms into palladium-nitrogen-carbon catalysts had several positive effects, like keeping the power dense cells stable for nearly 6,000 hours. Catalysts are substances that increase the rate of reaction without underdoing permanent chemical change itself.  

Since motor vehicles with combustion engines are a main source that emits the greenhouse gas C02, alternative energy conversion devices using fuel from renewable and sustainable sources are urgently needed. Feng said that direct-ethanol fuel cells have the potential to replace gasoline and diesel-based energy conversion systems as power sources.  

Currently, Feng and collaborators are soliciting funding to develop prototypes of DEFC units for portable devices and vehicles. He believes that if successful, this device can be used for commercialization in five years and with more industrial collaborators, DEFC vehicles can be implemented in 10 years.  

Regarding the product, ethanol consists of carbon, hydrogen and oxygen and is the active ingredient in alcoholic drinks, which can be derived from many sources like corn, wheat, grain sorghum, barely, sugar cane and sweet sorghum. In the U.S., most of the ethanol produced is made in the Midwest, most typically from corn.  

Feng explained that because a fuel cell relies on hydrogen and other fuels to cleanly and efficiently produce electricity, a wide range of fuels and feedstocks can serve systems as large as a utility power plant and as small as a laptop. With infrastructure already in place for producing and distributing ethanol, a benefit of this process is that plants absorb atmospheric carbon dioxide. Ethanol can also deliver more energy per kilogram than other fuels like methanol or pure hydrogen, which makes DEFC an attractive option for replacing internal combustion engines.  

Development of DEFC has significantly lagged due to low efficiency of DEFC, the costs related to catalysts and the risk of catalyst poisoning from carbon monoxide produced in reactions inside the fuel cell. In response to these problems, collaborators developed high-performance palladium alloy catalysts that use less of the precious metal than current palladium-based catalysts.  

Feng summarized that his team showed how introducing fluorine atoms into palladium nitrogen-carbon catalysts modifies the environment around the palladium, and improves both activity and durability for two important reactions in the cell: the ethanol oxidation reaction and the oxygen reduction reaction. He concluded that advanced synchrotron X-ray spectroscopy characterizations made at Argonne suggest that fluorine atom introduction creates a more nitrogen-rich palladium surface, which is favorable for catalysis. Durability is enhanced by inhibiting palladium migration and decreasing carbon corrosion.