Sputter-Deposited Ruthenium Nitrides for Electrochemical Nitrogen Fixation to Ammonia under Ambient Conditions

Electrochemical nitrogen reduction reaction (eNRR) under ambient conditions offers a promising route for ammonia synthesis, although it currently suffers from slow kinetics and competing hydrogen evolution. Transition metal nitrides (TMNs) enable efficient nitrogen activation via the Mars-van Krevelen mechanism; however, effectively suppressing nitrogen leaching under electrochemical conditions remains challenging. Here, we report a nanostructured ruthenium nitride (RuN) catalyst synthesized via magnetron sputtering, demonstrating its application for eNRR for the first time. Structural characterization confirms a zincblende-like RuN phase, while surface properties (i.e., roughness and wettability) are tuned by the deposition duration. The optimal catalyst achieved an ammonia yield of 3.0 × 10^-10 mol cm^-2 s^-1 at -0.3 V vs RHE and a Faradaic efficiency of 6.1% at -0.1 V vs RHE in a 0.1 mol L^-1 KOH electrolyte, surpassing most reported ambient TMN catalysts. These findings underscore the promise of metal nitride-based electrocatalysts and provide insights into the rational design of next-generation catalysts for sustainable nitrogen fixation.