Electrochemical synthesis of ammonia
is deemed as an alternative
to the fossil-fuel-driven Haber–Bosch (HB) process, in which
Li-mediated nitrogen reduction (LiNR) is the most promising scheme.
Continuous lithium-mediated nitrogen reduction for ammonia synthesis
(C-LiNR) has recently been reported in high-level journals with many
foggy internal reactions. Synthesizing ammonia in a separate way may
be profitable for understanding the mechanism of LiNR. Herein, an
intermittent lithium-mediated nitrogen reduction for ammonia synthesis
(I-LiNR) was proposed, three steps required for I-LiNR were achieved
in the cathode chamber of a Li–N2 battery. Discharge,
stand, and charge in the Li–N2 battery correspond
to N2 lithification, protonation, and lithium regeneration,
respectively. It can also realize the quasi-continuous process with
practical significance because it could be carried out through identical
batteries. Products such as Li3N, LiOH, and NH3 are detected experimentally, which demonstrate a definite reaction
pathway. The mechanism of the Li–N2 battery, the
Li-mediated synthesis of ammonia, and LiOH decomposition are explored
through density functional theory calculations. The role of Li in
dinitrogen activation is highlighted. It expands the range of LiOH-based
Li–air batteries and may guide the study from Li–air
to Li–N2; attention has been given to the reaction
mechanism of Li-mediated nitrogen reduction. The challenges and opportunities
of the procedure are discussed in the end.