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Title: Nitrogenase-mimic iron-containing chalcogels for photochemical reduction of dinitrogen to ammonia

A nitrogenase-inspired biomimetic chalcogel system comprising double-cubane [Mo2Fe6S8(SPh)3] and single-cubane (Fe4S4) biomimetic clusters demonstrates photocatalytic N2 fixation and conversion to NH3 in ambient temperature and pressure conditions. Replacing the Fe4S4 clusters in this system with other inert ions such as Sb3+, Sn4+, Zn2+ also gave chalcogels that were photocatalytically active. Finally, molybdenum-free chalcogels containing only Fe4S4 clusters are also capable of accomplishing the N2 fixation reaction with even higher efficiency than their Mo2Fe6S8(SPh)3-containing counterparts. In this study, our results suggest that redox-active iron-sulfide–containing materials can activate the N2 molecule upon visible light excitation, which can be reduced all of the way to NH3 using protons and sacrificial electrons in aqueous solution. Evidently, whereas the Mo2Fe6S8(SPh)3 is capable of N2 fixation, Mo itself is not necessary to carry out this process. The initial binding of N2 with chalcogels under illumination was observed with in situ diffuse-reflectance Fourier transform infrared spectroscopy (DRIFTS). 15N2 isotope experiments confirm that the generated NH3 derives from N2. Density functional theory (DFT) electronic structure calculations suggest that the N2 binding is thermodynamically favorable only with the highly reduced active clusters. Finally, the results reported herein contribute to ongoing efforts of mimicking nitrogenase in fixing nitrogen and pointmore » to a promising path in developing catalysts for the reduction of N2 under ambient conditions.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Northwestern Univ., Evanston, IL (United States)
  2. Univ. of Ioannina, Ioannina (Greece)
Publication Date:
Grant/Contract Number:
SC0001059
Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 113; Journal Issue: 20; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Northwestern Univ., Evanston, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; nitrogenase mimics; chalcogel; N2 fixation; ammonia synthesis; photocatalytic
OSTI Identifier:
1250547
Alternate Identifier(s):
OSTI ID: 1347972