Ammonia (NH3) is an essential
commodity manufactured
by the chemical industry. However, it is still mainly synthesized
via the traditional Haber–Bosch process, which is energy consuming
and produces large amounts of CO2. As one of the most promising
alternatives, the electrochemical reduction of nitrogen (N2) under mild reaction conditions exhibits only low efficiency for
NH3 synthesis because of the low water solubility of N2 and the high energy of the triple bond in molecular N2. Here, we use an N2 fixation strategy of “oxidation–reduction”
based on a coupled plasma catalysis and electrocatalytic system. First,
a perovskite LaFeO3 catalyst is used in a nonthermal plasma
to oxidize N2 to nitrate/nitrite (NO
x
–), which quickly dissolves in water for
activation in the next step. The theoretical calculations indicate
that the LaFeO3 with rich surface-reactive oxygen species
has better activity and stability in the reaction than poor surface-reactive
oxygen species, thereby enhancing the increase of NO
x
– production. Then NO
x
– is electrochemically reduced to NH3 using a Cu+/Cu0 catalyst with considerable
activity (3.0 mg h–1 cm–2) and
high faradaic efficiency (83.2%). The process only requires air and
water as reactants. This strategy could provide a new and efficient
pathway for NH3 synthesis directly from the air.