Ambient ammonia synthesis from air via tandem water microdroplets–driven oxidation and pulsed photoelectrochemical reduction

Artificial N2 reduction offers a sustainable approach to green NH3 synthesis, but the practical implementation is challenged by N2 activation and competing hydrogen evolution. Photoelectrochemical nitrate and nitrite (NOx-, x = 2 and 3) reduction with favorable thermodynamics represents a promising alternative for NH3 production, provided that NOx- can be supplied from the atmosphere. Here, through leveraging water microdroplet chemistry and dynamic photoelectrode-electrolyte interface engineering, we report a tandem air-NOx--NH3 conversion system that integrates catalyst-free N2 oxidation with pulsed photoelectrochemical NOx- reduction (mNOR-pPNOxR). The system achieves efficient and selective NH3 production with a yield rate of 24.5 μmol cm-2 h-1 at -0.2 VRHE, which are two to three orders of magnitude higher than conventional photo/electrocatalytic N2 fixation. This study introduces insights for decentralized, on-demand ammonia production from air and water and broadens horizons of microdroplet chemistry and pulse strategy for sustainable chemical manufacturing.