Nanosheets Catalyze Nitrogen Fixation

A research team in China has invented a light-harvesting layered semiconductor nanosheet that could one day significantly reduce the energy required for chemically reducing nitrogen to ammonia. Converting N₂ to NH₃ via the iron-catalyzed Haber-Bosch process is one of the most important industrial chemical reactions. But splitting N₂ and preparing hydrogen via steam reforming of methane at high temperature and pressure make it one of the most energy-intensive processes. Lizhi Zhang of Central China Normal University and coworkers designed a layered BiOBr catalyst with oxygen vacancies that is ideal for binding N₂ molecules. When the researchers shine visible light on the nanosheet surface the semiconductor generates electrons to reduce adsorbed N₂ while at the same time it oxidizes water solvent molecules to generate H⁺ and O₂. Overall, the process couples nitrogen and hydrogen to make NH₃ at room temperature and atmospheric pressure with better efficiency than previously reported semiconductor systems (J. Am. Chem. Soc. 2015, DOI: 10.1021/jacs.5b03105). “Although photocatalytic reduction is unlikely to replace the Haber-Bosch process at present,” the researchers write, “this study might open up a new vista.”