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

Abstract

The fixation of atmospheric N 2 to NH 3 is an essential process for sustaining life. One grand challenge is to develop efficient catalysts to photofix N 2 under ambient conditions. Herein we report an all-inorganic catalyst, Au nanocrystals anchored on ultrathin TiO 2 nanosheets with oxygen vacancies. It can accomplish photodriven N 2 fixation in the “working-in-tandem” pathway at room temperature and atmospheric pressure. The oxygen vacancies on the TiO 2 nanosheets chemisorb and activate N 2 molecules, which are subsequently reduced to NH 3 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 NH 3 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 N 2 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 N 2 fixation through a less energy-demanding photochemical process compared to the industrial Haber–Bosch process.