(446f) Promoting Reliable Electrocatalytic N2 Reduction

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.