Mass-Transport Effects in the Lithium Redox-Mediated Nitrogen Reduction Reaction
Ngoc-Trung Nguyen1, Syed Asad Abbas1, Andrew Nattestad2
1School of Chemistry, Monash University, Clayton, Victoria3800, Australia.
Journal of the American Chemical Society
|April 29, 2026
Summary
Optimizing ammonia electrosynthesis via lithium redox-mediated nitrogen reduction reaction (Li-NRR) requires careful control of mass transport and electrolyte conditions. Simply increasing flow rate does not guarantee higher ammonia production or efficiency.
Area of Science:
- Electrochemistry
- Chemical Engineering
- Materials Science
Background:
- High-performance ammonia electrosynthesis is crucial for sustainable chemical production.
- The lithium redox-mediated nitrogen reduction reaction (Li-NRR) offers a promising pathway for ammonia synthesis.
- Understanding the interplay between reaction kinetics and mass transport is vital for optimizing Li-NRR systems.
Purpose of the Study:
- To investigate the Li-NRR and associated processes under varying mass-transport conditions.
- To elucidate the influence of electrolyte composition and flow rate on Li-NRR performance.
- To identify optimal conditions for maximizing ammonia production and faradaic efficiency.
Main Methods:
- Development and utilization of a wall-jet electrode flow cell.
- Systematic investigation of Li-NRR kinetics, Li+ reduction, Li3N and LiH formation, and electrodeposit protonation.
- Analysis of mass-transport effects using different electrolytes (LiBF4, LiNTf2) and proton carriers (C2H5OH) in tetrahydrofuran.
Main Results:
- Mass-transport effects on Li-NRR are electrolyte-dependent.
- 1 M LiBF4 showed high mass-transport sensitivity, achieving 75% faradaic efficiency at optimal Li3N-to-LiH ratio.
- 2 M LiNTf2 performance depended on Li3N:LiH ratio but showed minimal mass-transport sensitivity due to cathode passivation.
- 1 M LiNTf2 performance was dominated by side reactions, not Li-NRR.
Conclusions:
- Intensifying mass transport alone does not improve ammonia production rates or faradaic efficiency in Li-NRR systems.
- Optimizing flow rate requires re-adjusting N2 pressure, proton carrier concentration, and electrolyte composition.
- Tailoring electrolyte conditions is key to efficient and selective ammonia electrosynthesis.
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