Atomic Scale Cooperativity of Alloy Nanostructures for Efficient Nitrate Electroreduction to Ammonia in Neutral Media

Electrochemical nitrate reduction reaction (NO₃RR) offers a route to balanced nitrogen cycle and sustainable ammonia production. However, unsatisfied performance in neutral media arising from competitive hydrogen evolution reaction and inefficient hydrogenation impede the further applications of NO₃RR. Herein, the rational design of RuNi alloy nanostructures is reported. Benefited from the synergism effect between Ru and Ni, Ru₂₀Ni₈₀ alloy exhibits a high NH₃ Faradaic efficiency of 98.02% at −0.35 V (vs reversible hydrogen electrode (RHE)) and a large NH₃ yield rate of 27.88 mg mg_cat⁻¹ h⁻¹ at −0.65 V (vs RHE). Importantly, the atomic scale cooperation between Ru and Ni active sites endows RuNi alloy a close-to-unity NH₃ selectivity via HNO^* pathway. Theoretical calculations have revealed that the interactions between Ru and Ni optimize the electronic structures of Ru₂₀Ni₈₀ alloy, where Ru sites with enhanced electroactivity improve the generation of active hydrogens and more electron-rich Ni sites facilitate the reduction of nitrate. Accordingly, the adsorption strengths of key intermediates become stronger and the energy barriers of NO₃RR are reduced to guarantee efficient NO₃RR. Furthermore, a flow-type reactor coupled with coprecipitation is established to achieve continuous NH₃ generation and recovery as struvite. © 2024 Wiley-VCH GmbH.