A new process using light to reduce dinitrogen into ammonia, the main ingredient in chemical fertilizers, could inspire development of new, more sustainable processes. According to researchers at the Energy Department's National Renewable Energy Laboratory (NREL), photochemical (photon) energy can serve as a substitute for the adenosine 5'-triphosphate (ATP)-dependent electron transfer mechanism typically used in biology to drive nitrogenase to reduce dinitrogen (N2) to ammonia (NH3).
Scientists at NREL worked with researchers at Utah State University, University of Colorado Boulder, and Montana State University.
"Not only were we able to prove the light-driven process successful for the first time, but the rates of ammonia production were shown to be a good approximation to those of the ATP-dependent reaction, at 60-70%," said NREL Research Scientist Paul King.
The study entitled: "Light-driven dinitrogen reduction catalyzed by a CdS:nitrogenase MoFe protein biohybrid," appears in the journal Science, and was authored by Katherine A. Brown, Derek F. Harris, Molly B. Wilker, Andrew Rasmussen, Nimesh Khadka, Hayden Hamby, Stephen Keable, Gordana Dukovic, John W. Peters, Lance C. Seefeldt, and Paul W. King.
The researchers showed that cadmium sulfide (CdS) nanocrystals can be used to harvest light, turning the energy from that light to energize electrons with sufficient potential to propel the reduction of N2 into ammonia, which takes place within the nitrogenase molybdenum iron (MoFe) protein. The new method essentially replaces the ATP hydrolysis-dependent enzymatic process with CdS nanorod light-harvesting and energy conversion.
"Using light harvesting to drive difficult catalytic reactions has the potential to create new, more efficient chemical and fuel production technologies," said NREL Research Scientist Katherine Brown. "Light driven N2 reduction has been done before, just at very, very low rates and not by nitrogenase. We did it with nitrogenase and obtained much higher yields and rates."
NREL's Laboratory-Directed Research and Development programme provided the funding.
"We followed an idea to create new science that we expect will make a significant impact on the industrial and scientific production of ammonia," King added. "In the case of this study, the type of funding allowed us to try something that we hadn't tested before, and it paid off."
Edited from press release by Angharad Lock
Read the article online at: https://www.hydrocarbonengineering.com/petrochemicals/22042016/nrel-reduces-dinitrogen-into-ammonia-using-light-48/