Synthesis of hydroxylamine from air and water via a plasma-electrochemical cascade pathway

Hydroxylamine is an important nitrogenous feedstock for the chemical industry. Conventional hydroxylamine synthesis methods utilize ammonia as the nitrogen source and require harsh reaction conditions, leading to unfavourable environmental footprint. Here we develop a plasma-electrochemical cascade pathway (PECP) powered by electricity for sustainable hydroxylamine synthesis directly from ambient air and water at mild conditions. In the first step, the plasma treatment of ambient air and water delivers a nitric acid solution with a concentration of up to 120.1 mM. Subsequently, the obtained nitric acid is selectively electroreduced to hydroxylamine using a bismuth-based catalyst. The faradaic efficiency for hydroxylamine reached 81.0% at −1.0 V versus reversible hydrogen electrode. As a result, this PECP method achieves a high hydroxylamine yield rate of 713.1 μmol cm⁻² h⁻¹ with a selectivity of 95.8%. Notably, both steps of the PECP method are operated at room temperature. Overall, our work provides a viable approach for efficient hydroxylamine synthesis from simpler feedstock at milder conditions, contributing to the sustainability transformation of the chemical industry.