Combined, time-resolved, neutron reflectometry and X-ray diffraction analysis of dynamic SEI formation during electrochemical N reduction

One means of improving performance for electrochemical ammonia production through the Li-mediated N 2 reduction reaction (Li-NRR) is by cycling the current driving the reaction between open-circuit conditions and periods of applied current density. Herein, we have investigated the dynamics of the el...

Full description

Saved in:
Bibliographic Details
Published in:Energy & environmental science 2023-08, Vol.16 (8), p.3391-346
Main Authors: Blair, Sarah J, Doucet, Mathieu, Niemann, Valerie A, Stone, Kevin H, Kreider, Melissa E, Browning, James F, Halbert, Candice E, Wang, Hanyu, Benedek, Peter, McShane, Eric J, Nielander, Adam C, Gallo, Alessandro, Jaramillo, Thomas F
Format: Article
Language:
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:One means of improving performance for electrochemical ammonia production through the Li-mediated N 2 reduction reaction (Li-NRR) is by cycling the current driving the reaction between open-circuit conditions and periods of applied current density. Herein, we have investigated the dynamics of the electrode-electrolyte interface under Li-NRR conditions during current cycling using in situ time-resolved neutron reflectometry and grazing-incidence synchrotron X-ray diffraction. During cycling, measured neutron reflectivity curves indicated bilayer formation in which Li-containing species such as LiOH, Li 2 O, and small quantities of Li 3 N and metallic Li primarily appeared in a thin layer at the cathode surface, above which formed a much larger, porous, 'solid-electrolyte interface' (SEI) layer. Upon return to open-circuit conditions, Li-containing species quickly moved out of the thin layer, leaving a compact, stable layer of decomposition products underneath the SEI layer. This SEI layer concomitantly filled with electrolyte or dissolved, becoming indistinguishable from the electrolyte via contrast in scattering-length density (SLD). During the second current cycle, Li-containing species again preferentially deposited directly atop the cathode, with the thick SEI-like layer again appearing within a minute. This SEI layer exhibited a lower SLD more quickly than in the first cycle, which might suggest that Li-containing species become distributed within the porous SEI layer. Thus, these time-resolved observations of SEI and plated layers during current cycling suggest that benefits associated with return to open-circuit conditions between periods of applied current density may be related to the concomitant loss of Li-containing species from a thin layer at the cathode surface into a porous SEI layer that becomes filled with electrolyte or dissolves. In situ neutron reflectometry and GI-XRD reveal the dynamics of SEI formation and layer composition during Li-NRR with current cycling.
ISSN:1754-5692
1754-5706
DOI:10.1039/d2ee03694k