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Innovative, Green Method for Synthesizing Ammonia Under Milder Conditions

Researchers from UCF have collaborated with colleagues from Virginia Tech to devise an innovative, “green” technology for synthesizing ammonia that might assist in ensuring more sustainable supplies to the exploding world population.

Image credit: Karen Norum

This new approach can facilitate ammonia production using renewable energy, such as electricity generated from solar or wind. Basically, this new approach can help advance a sustainable development of our human society.

Xiaofeng Feng, Physics Assistant Professor

Ammonia, a compound containing nitrogen and hydrogen, is vital to all forms of life on Earth and is an important constituent of the majority of the fertilizers used for food production. From the time of World War I, the Haber-Bosch method has been primarily employed to synthesize the ammonia used in fertilizers. Apart from being fossil-fuel and energy intensive, this method could not be improved to date due to significant obstacles.

The innovative methodology of the team has been described in the Nature Communications journal published online on May 15, 2018.

The major hindrance in the production of ammonia is the high energy barrier for the activation of nitrogen molecules. For achieving a high reaction rate of the chemical process, nitrogen and hydrogen molecules should be heated to a temperature of 662 to 1022 °F at a pressure of 2200−5100 pounds per square inch in the presence of iron-based catalysts. Very high temperature and pressure conditions are mandatory for the chemical reaction to take place.

There have been various attempts to synthesize ammonia under less severe conditions, and one such attempt is the use of electrical energy. For performing an electrochemical process at room temperature, the reaction with water as the hydrogen source is driven by using active electrons; however, efficient use of the electrons that pass through an electrode is not possible and the reaction rate is very low.

Our research discovered a new mechanism whereby electrons can be more efficiently used via the catalyst of palladium hydride. This new approach may not only provide a new route for ammonia synthesis with minimal electrical energy but also inspire peer researchers to use the principle to address other challenging reactions for renewable energy conversion, such as turning carbon dioxide into fuels.

Xiaofeng Feng, Physics Assistant Professor

According to Hongliang Xin, an assistant professor at Virginia Tech and co-author of the study, there is much more to find out in this new field of research.

This is a very exciting research for converting nitrogen to ammonia at room temperature. Quantum chemical simulations have suggested a unique reaction pathway for the palladium catalyst with a lower energy barrier. However, the detailed mechanism, particularly its competition with electron-stealing hydrogen evolution and effect of operating voltage, is still largely unknown.

Hongliang Xin, Assistant Professor at Virginia Tech

Postdoctoral scholar Jun Wang and graduate student Lin Hu from Feng’s research group at UCF, chemistry Assistant Professor Gang Chen from UCF, and postdoctoral scholar Liang Yu from Xin’s research group at Virginia Tech are the other contributors to the study.

The UCF Startup Fund, the American Chemical Society Petroleum Research Fund, and the National Science Foundation CBET Catalysis Program supported the study. Synchrotron beam time has been granted for the team at the Department of Energy’s SLAC National Accelerator Laboratory facility in California this summer for further analysis of the mechanism.

Feng joined UCF’s physics department and the Energy Conversion and Propulsion Cluster in 2016 with joint appointments in the Department of Chemistry and the Department of Materials Science and Engineering. He has a doctorate in materials science and engineering from the University of California at Berkeley and was a postdoctoral scholar at Stanford University.

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