EnergyMaking ethanol without corn or other plants
Ethanol today is produced at high-temperature fermentation facilities that chemically convert corn, sugarcane, and other plants into liquid fuel. Growing crops for biofuel, however, requires thousands of acres of land and vast quantities of fertilizer and water. In some parts of the United States, it takes more than 800 gallons of water to grow a bushel of corn, which, in turn, yields about three gallons of ethanol. Stanford scientists have created a copper-based catalyst that produces large quantities of ethanol from carbon monoxide gas at room temperature.
Stanford University scientists have found a new, highly efficient way to produce liquid ethanol from carbon monoxide gas. This promising discovery could provide an eco-friendly alternative to conventional ethanol production from corn and other crops, say the scientists.
Their results are published in the April 9 advanced online edition of the journal Nature.
“We have discovered the first metal catalyst that can produce appreciable amounts of ethanol from carbon monoxide at room temperature and pressure — a notoriously difficult electrochemical reaction,” said Matthew Kanan, an assistant professor of chemistry at Stanford and coauthor of the Nature study.
A Stanford University release reports that most ethanol today is produced at high-temperature fermentation facilities that chemically convert corn, sugarcane, and other plants into liquid fuel. Growing crops for biofuel, however, requires thousands of acres of land and vast quantities of fertilizer and water. In some parts of the United States, it takes more than 800 gallons of water to grow a bushel of corn, which, in turn, yields about three gallons of ethanol.
The new technique developed by Kanan and Stanford graduate student Christina Li requires no fermentation and, if scaled up, could help address many of the land- and water-use issues surrounding ethanol production today. “Our study demonstrates the feasibility of making ethanol by electrocatalysis,” Kanan said. “But we have a lot more work to do to make a device that is practical.”
Novel electrodes
Two years ago, Kanan and Li created a novel electrode made of a material they called oxide-derived copper. They used the term “oxide-derived” because the metallic electrode was produced from copper oxide.
“Conventional copper electrodes consist of individual nanoparticles that just sit on top of each other,” Kanan said. “Oxide-derived copper, on the other hand, is made of copper nanocrystals that are all linked together in a continuous network with well-defined grain boundaries. The process of transforming copper oxide into metallic copper creates the network of nanocrystals.”
For the Nature study, Kanan and Li built an electrochemical cell — a device consisting of two electrodes placed in water saturated with carbon monoxide gas. When a voltage is applied across the electrodes of a conventional cell, a current flows and water is converted to oxygen gas at one electrode (the anode) and hydrogen gas at the other electrode (the cathode). The challenge was to find a cathode that would reduce carbon monoxide to ethanol instead of reducing water to hydrogen.
