Excitation-Rate Determines Product Stoichiometry In Photochemical Ammonia Production by CdS Quantum Dot-Nitrogenase MoFe Protein Complexes

Authors

Katherine A. Brown, National Renewable Energy Laboratory
Jesse Ruzicka, University of Colorado Boulder
Hayden Kallas, Utah State University
Bryant Chica, National Renewable Energy Laboratory
David W. Mulder, National Renewable Energy Laboratory
John W. Peters, Washington State University Pullman
Lance C. Seefeldt, Utah State UniversityFollow
Gordana Dukovic, University of Colorado Boulder
Paul W. King, National Renewable Energy Laboratory

Document Type

Article

Journal/Book Title

ACS Catalysis

Publication Date

9-10-2020

Publisher

American Chemical Society

Volume

10

Issue

19

First Page

11147

Last Page

11152

Abstract

The reduction of dinitrogen (N2) to ammonia (NH3) by nitrogenase MoFe protein is coupled to chemically driven electron transfer by nitrogenase Fe protein, where H2 is an obligatory side product. Direct coupling of light-absorbing semiconductor nanocrystals to MoFe protein enables NH3 production from photoexcited electron transfer, replacing Fe protein. Production of H2 and NH3 was measured for CdS quantum dot (QD) MoFe protein complexes illuminated under different excitation rates. 15N-labeling of NH3 production combined with background-corrected H2 production enabled determination of MoFe protein catalysis products. The turnover rates of H2 and NH3 increased with excitation rate, with distinct kinetic responses that show the electron demand for NH3 requires higher excitation rates to overcome the more favored H2 production.

Recommended Citation

Brown, K. A., Ruzicka, J., Kallas, H., Chica, B., Mulder, D. W., Peters, J. W., Seefeldt, L. C., Dukovic, G., and King, P. W. (2020) Excitation-Rate Determines Product Stoichiometry in Photochemical Ammonia Production by CdS Quantum Dot-Nitrogenase MoFe Protein Complexes. ACS Catal. 10, 11147–11152.