Active catalytic site in methanol synthesis exposed

Industrial catalysts composed of copper and zinc oxide sitting on top of alumina can add hydrogen to carbon monoxide and CO₂ to create methanol. But these catalysts have shortcomings, according to Ping Liu, a chemist at Brookhaven National Laboratory. The Cu-ZnO catalysts are not efficient or selective in producing methanol, and the reactions require high temperatures and high reactant pressures. What’s more, Liu said at the ACS meeting last week, chemical details of the active catalytic site remain elusive. Various researchers have argued that highly active Zn-Cu alloy species are the key catalytic players. In contrast, Liu’s new work suggests that the action occurs at the atomic interface between ZnO and Cu (Science 2017, DOI: 10.1126/science.aal3573). To reach that conclusion, Liu and coworkers prepared several types of Cu and ZnO reference catalysts, including one made of Zn nanoparticles deposited on copper and another with ZnO nanoparticles on copper. They analyzed and directly compared the CO₂-to-methanol chemistry of all the catalysts using photoelectron spectroscopy and computational methods. The analyses showed that Cu-ZnO surface species are the most active form of the catalyst. They also showed that the Zn-Cu species don’t remain stable under reaction conditions. Instead, they react with oxygen and form Cu-ZnO.