Lithium-Mediated Electrochemical Nitrogen Reduction: Tracking Electrode–Electrolyte Interfaces via Time-Resolved Neutron Reflectometry

Sarah J. Blair, Mathieu Doucet, James F. Browning, Kevin Stone, Hanyu Wang, Candice Halbert, Jaime Aviles Acosta, Jose Zamora Zeledon, Adam C. Nielander, Alessandro Gallo, Thomas F. Jaramillo
Year of publication: 
ACS Energy Letters

We employed time-resolved, in situ neutron reflectometry to observe a dynamic electrode–electrolyte interface under conditions relevant to Li-mediated electrochemical N2 reduction reaction (NRR). This method leverages the sensitivity of neutrons to Li and fast time resolution (∼1 min) to observe the formation of a layer containing Li species at the electrode surface within minutes of applying a current density (−0.1 mA/cm2). Notably, within the first 6 min, we did not observe a solid-electrolyte interphase (SEI) distinct from this layer, providing insight into recent reports demonstrating performance advantages of short current cycles interspersed with open-circuit conditions for NRR. At longer time scales following chronopotentiometry (∼2 h), a multilayer SEI remained, though the presence of Li was not evident, indicating that the layers containing Li species observed over shorter time scales degrade almost entirely under open-circuit conditions, leaving SEI layers consisting of electrolyte decomposition products. We thus present the first application of neutron reflectometry toward the NRR─through fast time-resolved measurements, we have enabled a path toward understanding the electrochemical NRR as well as dynamic systems across a wide range of energy technologies.

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