Near-Unity Nitrate to Ammonia conversion via reactant enrichment at the solid-liquid interface

Abstract

Abstract Electroreduction of nitrate (NO3 ‒) to ammonia (NH3) is a promising approach for addressing energy challenges. However, the activity is limited by NO3 ‒ mass transfer, particularly at reduction potential, where an abundance of electrons on the cathode surface repels NO3 ‒ from the inner Helmholtz plane (IHP). This constraint becomes pronounced as NO3 ‒ concentration decreases, impeding practical applications in the conversion of NO3 ‒-to-NH3. Herein, we propose a generic strategy of catalyst bandstructure engineering for the enrichment of negatively charged ions through solid-liquid (S-L) junction-mediated charge rearrangement within IHP. Specifically, during NO3 ‒ reduction, the formation of S-L junction induces hole transfer from Ag-doped MoS2 (Ag-MoS2) to electrode/electrolyte interface, triggering abundant positive charges on the IHP to attract NO3 ‒. Thus, Ag-MoS2 exhibits a ~ 28.6-fold NO3 ‒ concentration in the IHP than the counterpart without junction, and achieves near-100% NH3 Faradaic efficiency with an NH3 yield rate of ~20 mg h‒1 cm‒2 under ultralow NO3 ‒ concentrations.