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

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. 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:

Liu, Jian ^[1]; Kelley, Matthew S. ^[1]; Wu, Weiqiang ^[1]; Banerjee, Abhishek ^[1]; Douvalis, Alexios P. ^[2]; Wu, Jinsong ^[1]; Zhang, Yongbo ^[1]; Schatz, George C. ^[1]; Kanatzidis, Mercouri G. ^[1]

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+ Show Author Affiliations

1. Department of Chemistry, Northwestern University, Evanston, IL 60208,, Argonne-Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL 60208,
2. Department of Physics, University of Ioannina, 45110 Ioannina, Greece

Publication Date:

Mon May 02 00:00:00 EDT 2016

Research Org.:

Northwestern Univ., Evanston, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1250547

Alternate Identifier(s):

OSTI ID: 1347972

Grant/Contract Number:  

SC0001059

Resource Type:

Published Article

Journal Name:

Proceedings of the National Academy of Sciences of the United States of America

Additional Journal Information:

Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 113 Journal Issue: 20; Journal ID: ISSN 0027-8424

Publisher:

Proceedings of the National Academy of Sciences

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; nitrogenase mimics; chalcogel; N2 fixation; ammonia synthesis; photocatalytic