Renewable ethanol from carbon dioxide

Most cars and trucks in the United States use a mixture of 90% gasoline and 10% renewable ethanol fermented from corn But 14 billion gallons of ethanol are needed annually for transportation, and millions of acres of farmland are needed to get this renewable ethanol A recent study from Stanford University shows that scientists have found a way to get ethanol without corn or other crops This promising technology consists of three basic components: water, carbon dioxide and electricity delivered through copper catalysts The results were published in the proceedings of the National Academy of Sciences (PNAs) "One of our long-term goals is to produce renewable ethanol in a way that does not affect the global food supply," said Thomas Jaramillo, associate professor at Stanford University's School of chemical engineering Scientists want to selectively convert carbon dioxide into higher value chemicals and fuels, such as ethanol and propanol, by designing copper catalysts, with little or no by-products But first, they need to have a clear understanding of how these catalysts work According to the PNAs study of copper crystal, Stanford University research team selected three different samples of crystalline copper, named copper (100), copper (111) and copper (751) The researchers used these numbers to describe the surface geometry of copper single crystals "Copper (100), copper (111) and copper (751) look almost the same, but the arrangement of atoms on their surfaces is quite different," said Christopher Hahn, a researcher from SLAC "The essence of our work is to understand how copper with different surface geometry affects the electrocatalytic performance." In previous studies, scientists have made a single crystal copper electrode with a size of only 1 mm2 "With such a small crystal, it's difficult to identify and quantify the molecules produced on the surface," Hahn explained "This makes it difficult to understand chemical reactions, so our goal is to make copper electrodes with a large single crystal surface quality In order to obtain larger samples, Hahn and his colleagues at SLAC have developed a novel way to grow single crystal copper on the large wafer of silicon wafer and sapphire, and successfully obtain copper (100), copper (111) and copper (751) films 600 times larger than the general single crystal on the surface of six square centimeters (source: Science Daily) catalytic performance in order to compare the electrocatalytic performance, the researchers put three large electrodes in water, exposed them to carbon dioxide gas and switched on the current The results show that the liquid products (such as ethanol and propanol) obtained from the electrode made of copper (751) are more selective than those from the electrode made of copper (100) or copper (111) when a specific voltage is applied This may be due to three different arrangements on the surface of the copper atom On the surface of copper (100) and copper (111), the atoms are closely stacked, in the form of squares and honeycombs, respectively The closer the atoms are arranged on the surface of copper, the more inert the surface is In the case of copper (751), however, the atoms on the surface are further apart, and it is easier to combine with reactants, such as carbon dioxide, to obtain ethanol and propanol The team at Stanford University (PNAs) finally hopes to develop a technology that can carry out industrial modeling and selectively produce fuel and chemicals Using carbon dioxide as raw material, it can be transformed into more valuable products through renewable power or direct light