Electrocatalytic nitrate-to-ammonia conversion with ~100% Faradaic efficiency via single-atom alloying

Converting nitrate to ammonia (NH₃) with the use of electricity produced from renewable energy provides an alternative and sustainable route for NH₃ synthesis under ambient conditions. However, due to the complex mechanism involving eight electrons and nine protons transfer processes in nitrate-to-ammonia conversion, reactions run with Cu-based catalysts for NH₃ often exhibit limited selectivity and yield. Here, we report a single-atom Ni-alloyed Cu catalyst that exclusively converts nitrate into NH₃ with a maximum Faradaic efficiency of ~100% and a yield rate of 326.7 μmol h⁻¹ cm⁻² at − 0.55 V versus reversible hydrogen electrode (RHE). X-ray absorption fine structure evidence and density functional theory calculations reveal that the activated single Ni atom on the Cu catalyst regulates the third protonation step of the electrocatalytic nitrate reduction reaction (eNO₃^-RR) and increases the interaction between the Ni atom and the crucial NOOH* intermediate, thus decreasing the limiting potential and inhibiting byproduct formation. A rough estimation suggests that the price of fertilizer produced by this single-atom alloyed catalyst through the eNO₃^-RR is competitive with the Haber-Bosch process.