Center for Molecular Electrocatalysis Pacific Northwest National Laboratory Richland Washington 99352 USA, Current address: College of Chemistry Central China Normal University Wuhan Hubei 430079 P. R. China
Center for Molecular Electrocatalysis Pacific Northwest National Laboratory Richland Washington 99352 USA
Ammonia is a promising candidate in the quest for sustainable, clean energy. With its capacity to serve as an energy carrier, the oxidation of ammonia opens avenues for carbon‐neutral approaches to address worldwide growing energy needs. We report the catalytic chemical oxidation of ammonia by an Earth‐abundant transition metal complex, trans ‐ [LFe II (MeCN) 2 ][PF 6 ] 2 , where L is a macrocyclic ligand bearing four N ‐heterocyclic carbene (NHC) donors. Using triarylaminium radical cations in MeCN, up to 182 turnovers of N 2 per Fe were obtained from chemical catalysis with an extremely low loading of the Fe catalyst (0.043 mM, 0.004 mol % catalyst). This chemical catalysis was successfully transitioned to mediated electrocatalysis for the oxidation of ammonia. Molecular electrocatalysis by the Fe catalyst and the mediator ( p ‐MeOC 6 H 4 ) 3 N exhibited a catalytic half‐wave potential ( E cat/2 ) of 0.18 V vs [Cp 2 Fe] +/0 in MeCN, and achieved 9.3 turnovers of N 2 at an applied potential of 0.20 V vs [Cp 2 Fe] +/0 at −20 °C in controlled‐potential electrolysis, with a Faradaic efficiency of 75 %. Based on computational results, the catalyst undergoes sequential oxidation and deprotonation steps to form [LFe IV (NH 2 ) 2 ] 2+ , and thereafter bimetallic coupling to form an N−N bond.
Liu, Liang, et al. "Oxidation of Ammonia Catalyzed by a Molecular Iron Complex: Translating Chemical Catalysis to Mediated Electrocatalysis." Angewandte Chemie, vol. 136, no. 41, Sep. 2024. https://doi.org/10.1002/ange.202402635
Liu, Liang, Johnson, Samantha I., Appel, Aaron M., & Bullock, R. Morris (2024). Oxidation of Ammonia Catalyzed by a Molecular Iron Complex: Translating Chemical Catalysis to Mediated Electrocatalysis. Angewandte Chemie, 136(41). https://doi.org/10.1002/ange.202402635
Liu, Liang, Johnson, Samantha I., Appel, Aaron M., et al., "Oxidation of Ammonia Catalyzed by a Molecular Iron Complex: Translating Chemical Catalysis to Mediated Electrocatalysis," Angewandte Chemie 136, no. 41 (2024), https://doi.org/10.1002/ange.202402635
@article{osti_2439784,
author = {Liu, Liang and Johnson, Samantha I. and Appel, Aaron M. and Bullock, R. Morris},
title = {Oxidation of Ammonia Catalyzed by a Molecular Iron Complex: Translating Chemical Catalysis to Mediated Electrocatalysis},
annote = {Abstract Ammonia is a promising candidate in the quest for sustainable, clean energy. With its capacity to serve as an energy carrier, the oxidation of ammonia opens avenues for carbon‐neutral approaches to address worldwide growing energy needs. We report the catalytic chemical oxidation of ammonia by an Earth‐abundant transition metal complex, trans ‐ [LFe II (MeCN) 2 ][PF 6 ] 2 , where L is a macrocyclic ligand bearing four N ‐heterocyclic carbene (NHC) donors. Using triarylaminium radical cations in MeCN, up to 182 turnovers of N 2 per Fe were obtained from chemical catalysis with an extremely low loading of the Fe catalyst (0.043 mM, 0.004 mol % catalyst). This chemical catalysis was successfully transitioned to mediated electrocatalysis for the oxidation of ammonia. Molecular electrocatalysis by the Fe catalyst and the mediator ( p ‐MeOC 6 H 4 ) 3 N exhibited a catalytic half‐wave potential ( E cat/2 ) of 0.18 V vs [Cp 2 Fe] +/0 in MeCN, and achieved 9.3 turnovers of N 2 at an applied potential of 0.20 V vs [Cp 2 Fe] +/0 at −20 °C in controlled‐potential electrolysis, with a Faradaic efficiency of 75 %. Based on computational results, the catalyst undergoes sequential oxidation and deprotonation steps to form [LFe IV (NH 2 ) 2 ] 2+ , and thereafter bimetallic coupling to form an N−N bond. },
doi = {10.1002/ange.202402635},
url = {https://www.osti.gov/biblio/2439784},
journal = {Angewandte Chemie},
issn = {ISSN 0044-8249},
number = {41},
volume = {136},
place = {Germany},
publisher = {Wiley Blackwell (John Wiley & Sons)},
year = {2024},
month = {09}}