Making Methanol From Carbon Dioxide And Sunlight

One of the sustainability challenges chemists face is finding an energy-efficient method for reducing industrial emissions of carbon dioxide. Trapping CO₂ in solutions of amines is one technique already being used, but it requires a significant amount of energy to strip the CO₂ from the amine and then compress and pump the CO₂ to a sequestration site. Another technique under development is using electrochemical cells to reduce CO₂ to value-added chemicals such as methanol. Emily E. Barton, David M. Rampulla, and Andrew B. Bocarsly of Princeton University have now created what appears to be the first such system that requires only visible light—and not an electrical socket—to make CH₃OH from CO₂ (J. Am. Chem. Soc. DOI: 10.1021/ja0776327). The researchers employed a light-driven gallium phosphide semiconductor electrode to reduce CO₂ bubbled through an aqueous solution of pyridine. The catalytic pyridine functions like an amine to bind CO₂ molecules and guide them to the electrode surface. The team used a mercury-xenon lamp to power the reaction in the lab, but sunlight should work just as well. Although Bocarsly is optimistic about the process, he says "it is still a large leap from the benchtop to a field application," such as real-time conversion of CO₂ to CH₃OH at a coal-fired power plant.