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Updated: May 16, 2025
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Electrochemically and Bioelectrochemically Induced Ammonium Recovery
Published on: January 22, 2015
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In Situ Neutron Reflectometry Reveals the Interfacial Microenvironment Driving Electrochemical Ammonia Synthesis.
Valerie A Niemann1,2, Mathieu Doucet3, Peter Benedek1,2
1Department of Chemical Engineering, Stanford University, 443 Via Ortega, Stanford, California 94305, United States.
Journal of the American Chemical Society
|April 2, 2025
Summary
Researchers used neutron reflectometry to study the solid-electrolyte interphase (SEI) during lithium-mediated nitrogen reduction. They found electrolyte choice impacts SEI structure, which evolves with cycling and is influenced by proton donors and solvents.
Area of Science:
- Materials Science
- Electrochemistry
- Surface Science
Background:
- Electrified interfaces are crucial for energy systems, but their complexity under operating conditions is a challenge.
- Understanding the solid-electrolyte interphase (SEI) nanoscale environment is vital for efficient ammonia production via lithium-mediated nitrogen reduction (Li-N2R).
Purpose of the Study:
- To investigate SEI formation and structure under Li-N2R conditions using time-resolved neutron reflectometry (NR).
- To compare the performance of LiBF4-based electrolytes versus LiClO4-based electrolytes in SEI formation.
- To elucidate the roles of proton donors and solvents in SEI evolution.
Main Methods:
- Time-resolved neutron reflectometry (NR) was employed to observe SEI formation in situ.
- Isotope contrast methods using d6-EtOH and d8-THF were utilized for time-resolved tracking of SEI growth.
- Neutron absorption was used to detect the presence of specific elements within the SEI.
Main Results:
- LiBF4-based electrolytes yielded a more defined SEI compared to LiClO4.
- The LiBF4-derived SEI initially presented as a thick, diffuse outer layer and a thin, compact inner layer under low current cycling.
- Increased current cycling led to the merging of these layers into a single-layer SEI.
- Proton donors influenced the inner SEI layer, while solvents affected the outer layer.
- Lithium dendritic growth was observed without a proton donor.
- Boron presence in the SEI was confirmed via neutron absorption.
Conclusions:
- The study reveals the dynamic, layered structure of the SEI under Li-N2R conditions, which is sensitive to electrolyte composition and cycling parameters.
- The findings highlight the importance of electrolyte design, particularly the role of the anion (BF4-), in forming a stable SEI.
- The developed in situ NR methods provide a powerful tool for studying interfacial phenomena in energy storage and conversion systems.
