(446f) Promoting Reliable Electrocatalytic N2 Reduction

Authors: 
Nielander, A. - Presenter, Stanford University
McEnaney, J. M., Stanford University
Schwalbe, J., Stanford University
Blair, S., Stanford University
Baker, J. G., Stanford University
Jaramillo, T. F., Stanford University
Electrocatalytic N2 reduction to NH3 has drawn significant interest as an alternative to the Haber Bosch process that could be readily coupled to renewable energy sources.We have evaluated electrocatalytic N2 reduction with a range of catalyst materials predicted to demonstrate measurable N2 reduction activity via DFT calculations. However, these experiments were hampered under both aqueous and non-aqueous electrolyte conditions by low selectivity toward non-H2 products and contamination from ambient NH3 sources, making it challenging to characterize the N2 reduction efficiency of low activity electrocatalysts.

We report our efforts to develop a standardized set of control experiments, equipment, and benchmarking protocols for the N2 reduction reaction based on the use of carefully purified, isotopically labeled 15N2 as the nitrogen source. In order to accommodate the need to efficiently detect both 14NH3 and 15NH3 in both aqueous and nonaqueous environments, we elaborated a frequency selective, quantitative NMR assay capable of detecting NH3in a range of compatible electrolytes, including ethanol, THF, DMSO, acetonitrile, propylene carbonate, and diethyl either. Using these methods, we have re-evaluated a number of electrocatalysts that we hypothesized to be active toward N2 reduction but did not find evidence for N2 reduction activity. Despite this, we believe there are still a number of strategies being pursued in the community that may lead to active N2 reduction catalysts, and we hope that the pursuit of rigorous methods being exhibited throughout the community will result in exciting new catalyst discoveries.

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