Crystal-structure engineering of Cu-Sn intermetallic enables accelerated proton transfer for nitrite-to-ammonia electroreduction.

Cu6Sn5 and Cu3Sn intermetallics were evaluated for electrocatalytic nitrite reduction reaction. Cu6Sn5 achieves an NH3 Faradaic efficiency of 98.23% at -0.3 V vs. RHE and an NH3 yield rate of 69.93 mg h-1 cm-2 at -0.7 V vs. RHE. Characterizations and theoretical calculations reveal that Cu6Sn5 provides a favorable interfacial environment for water activation and hydrogenation of nitrogen-containing intermediates. In a flow electrolyzer coupled with gas stripping and acid trapping, the Cu6Sn5 cathode operates stably at 500 mA cm-2 for 500 h and enables continuous production of NH4Cl fertilizer.