It is well known that ammonia is produced through a catalytic reaction at high temperature and pressure from pure nitrogen and hydrogen. This catalytic chemical process is a massive and high-energy-consuming process, but a very important one for nitrogen fixation. Here, we show a non-catalyzed one-step synthesis of ammonia from atmospheric air (nitrogen source) and water (hydrogen source), based on an interfacial reaction between the air plasma gas phase and the water phase, at 25 °C and atmospheric pressure. In the plasma/liquid interfacial reaction (P/L reaction), atomic nitrogen in both air plasma and nitrogen plasma first abstracts hydrogen from the water phase surface at the P/L interface, and then NH is produced without any catalyst. Transiently formed NH is reduced further at the water phase, affording NH₃, which then dissolves in the water phase. The P/L reaction may provide an alternative solution that enables both energy conservation and CO₂ emission reduction.

Cu-Sn alloy electrodes were prepared by simple electrodeposition method for the electrochemical reduction of CO₂ into CO and HCOO⁻. The alloy electrode surfaces provided good selectivity and efficiency in electrochemical CO₂ conversion because they provided appropriate binding energies between the metal and the reactive species obtained through CO₂ reduction. Therefore, product selectivity can be modulated by altering the Cu-Sn crystal structure of the electrode. Using the Cu-Sn alloy electrodes, electrochemical reduction was performed at applied potentials ranging from − 0.69 to − 1.09 V vs. reversible hydrogen electrode (RHE). During electrochemical CO₂ reduction, all the prepared Cu-Sn alloy electrodes showed prominent suppression of hydrogen evolution. In contrast, Cu₈₇Sn₁₃ has high selectivity for CO formation at all the applied potentials, with maximum faradaic efficiency (FE) of 60% for CO at − 0.99 V vs. RHE. On the other hand, Cu₅₅Sn₄₅ obtained a similar selectivity for electrodeposition of Sn, with FE of 90% at − 1.09 V vs. RHE. Surface characterization results showed that the crystal structure of Cu₈₇Sn₁₃ comprised solid solutions that play an important role in increasing the selectivity for CO formation. Additionally, it suggests that the selectivity for HCOO⁻ formation is affected by the surface oxidation state of Sn rather than by crystal structures like intermetallic compounds. The Cu-Sn alloy catalysts prepared by simple electrodeposition can control the selectivity for CO and HCOO⁻ formation by tuning its crystal structure. Surface analyses revealed that solid solutions and the oxidation state of Sn play an important role in the formation of CO and HCOO⁻ upon CO₂ reduction, respectively.

An interfacial reaction between the UV irradiated water phase (H˙ provides) and the electron-discharged nitrogen-gas phase (N atom provides) produces ammonia efficiently.