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

Jian Liu, Matthew S. Kelley, Weiqiang Wu, Abhishek Banerjee, Alexios P. Douvalis, Jinsong Wu, Yongbo Zhang, George C. Schatz*, Mercouri G. Kanatzidis

*Corresponding author for this work

Research output: Contribution to journalArticle

106 Scopus citations

Abstract

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. 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. The results reported herein contribute to ongoing efforts of mimicking nitrogenase in fixing nitrogen and point to a promising path in developing catalysts for the reduction of N2 under ambient conditions.

Original languageEnglish (US)
Pages (from-to)5530-5535
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume113
Issue number20
DOIs
StatePublished - May 17 2016

Keywords

  • Ammonia synthesis
  • Chalcogel
  • N fixation
  • Nitrogenase mimics
  • Photocatalytic

ASJC Scopus subject areas

  • General

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