(653a) Techniques for the Examination of Aqueous and Nonaqueous Electrocatalytic N2 Reduction | AIChE

(653a) Techniques for the Examination of Aqueous and Nonaqueous Electrocatalytic N2 Reduction

Authors 

Nielander, A. - Presenter, Stanford University
Niemann, V., Stanford University
Benedek, P., Stanford University
Cargnello, M., Stanford University
Jaramillo, T., Stanford University
The electrocatalytic N2 reduction reaction (N2RR) offers an alternative route to the traditional Haber-Bosch method for production of NH3. Electrifying NH3 synthesis promises a route to the decarbonization and decentralization of ammonia production, which currently accounts for >1% of our annual CO2 emissions. While there have been many studies examining the electrochemically-driven production of NH3 in aqueous electrolytes at low-temperature (≤ 50o C) and low-pressure (≤20 bar), lithium-mediated N2 electroreduction in nonaqueous electrolytes at low-T and low-P has emerged as a promising method for obtaining reliable selectivity and activity toward NH3. The proposed mechanism of this Li-mediated N2RR method entails the production of reduced-Li species as key intermediates — these Li species are well-known to be reactive, introducing challenges in controlling and studying the solid-electrolyte interphase (SEI) that plays a crucial role in dictating electrochemical behavior.

Herein, we review our efforts at SUNCAT to search for aqueous N2RR electrocatalysts, and we emphasize our recent work to improve our understanding of Li-mediated N2RR by developing complementary tools for operando interrogation of electrode-electrolyte interfaces. Among these tools, we are actively developing operando, time-resolved, neutron reflectometry as well as operando X-ray diffractometry (XRD). The neutron-based methods are inherently sensitive to Li and amorphous layers and serve as a complement to XRD methods that offer superior compositional insight for crystalline products. We have used them to observe the growth of apparent Li-rich SEI layers on one-minute timescales under applied current and under varying electrolyte conditions, opening an avenue to understand how changing electrolyte and potential/current conditions dictate the growth rate and composition of SEI layer formation from initial ‘t = 0 s’ conditions. Finally, we will discuss our recent exploration of directed chemical modification of the N2RR SEI layer using inorganic additives to attempt to exert control over the SEI and improve N2RR performance.