SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 65: Poster Session V: Solid-liquid interfaces: Reactions and electrochemistry II
O 65.5: Poster
Mittwoch, 3. März 2021, 10:30–12:30, P
Increasing stability, efficiency, and fundamental understanding of lithium-mediated electrochemical nitrogen reduction — •Vanessa J. Bukas1, Suzanne Z. Andersen1, Michael J. Statt2, Sarah G. Shapel1, Jakob B. Pedersen1, Kevin Krempl1, Mattia Saccoccio1, Debasish Chakraborty1, Jakob Kibsgaard1, Peter C. K. Vesborg1, Jens K. Nørskov1, and Ib Chorkendorff1 — 1Technical University of Denmark — 2Stanford University, USA
Lithium-mediated nitrogen reduction is a proven method to electrochemically synthesize ammonia; yet the instability and low efficiency of this process have so far limited its practical application. One major obstacle against improving the Li-mediated approach is that very little is understood about the mechanism. We develop here a kinetic model that highlights mass transport limitations as a very important factor to the resulting faradaic efficiency. Our results reproduce experimental trends for varying conditions of N2 pressure or H+ availability and show that the relative diffusion rates of reacting Li+, N2, and H+ species are key to selectively forming ammonia. On the basis of this understanding, we develop a potential-cycling strategy which can recover ‘catalytic’ high-energy electrons from unused metallic Li that was deposited at the electrode surface. This is shown experimentally to improve the stability of the system, alleviate the need for continuously replenishing the electrolyte with Li salts, and lead to a significant increase in both faradaic and energy efficiency [1].
[1] Andersen et al., Energy Environ. Sci. 13, 4291 (2020)