High-Efficiency “Working-in-Tandem” Nitrogen Photofixation Achieved by Assembling Plasmonic Gold Nanocrystals on Ultrathin Titania Nanosheets

The fixation of atmospheric N₂ to NH₃ is an essential process for sustaining life. One grand challenge is to develop efficient catalysts to photofix N₂ under ambient conditions. Herein we report an all-inorganic catalyst, Au nanocrystals anchored on ultrathin TiO₂ nanosheets with oxygen vacancies. It can accomplish photodriven N₂ fixation in the "working-in-tandem" pathway at room temperature and atmospheric pressure. The oxygen vacancies on the TiO₂ nanosheets chemisorb and activate N₂ molecules, which are subsequently reduced to NH₃ by hot electrons generated from plasmon excitation of the Au nanocrystals. The apparent quantum efficiency of 0.82% at 550 nm for the conversion of incident photons to NH₃ is higher than those reported so far. Optimizing the absorption across the overall visible range with the mixture of Au nanospheres and nanorods further enhances the N₂ photofixation rate by 66.2% in comparison with Au nanospheres used alone. This work offers a new approach for the rational design of efficient catalysts toward sustainable N₂ fixation through a less energy-demanding photochemical process compared to the industrial Haber-Bosch process.