Ultra-efficient N₂ electroreduction achieved over a rhodium single-atom catalyst (Rh₁/MnO₂) in water-in-salt electrolyte

Electrocatalytic nitrogen reduction reaction (NRR) is an appealing strategy for green ammonia synthesis. Despite tremendous efforts, current NRR performances of most catalysis systems remain far below the targets for practical applications. Herein, a highly active and selective NRR catalysis system is reported by using an Rh single-atom catalyst in water-in-salt electrolytes (WISE). The developed single-atomic Rh on MnO₂ (Rh₁/MnO₂) catalyst in 9 m K₂SO₄ presents a superior NH₃ yield of 271.8 μg h⁻¹ mg⁻¹ and Faradaic efficiency of 73.3%, far exceeding that in dilute electrolyte and representing one of the best NRR performances on record. Multiple operando XAS, in situ FTIR/Raman spectroscopic characterizations together with the theoretical calculations unravel that WISE enables Rh₁/MnO₂ to exhibit suppressed H₂ evolution, increased N₂ enrichment on catalyst surface, and enhanced N₂ activation/hydrogenation on active Rh sites.