Warm Non-equilibrium Plasma-Assisted Catalysis for Sustainable Ammonia Synthesis

Abstract

Ammonia is synthesized mainly through energy intensive Haber–Bosch process, a major source of global CO₂ emissions, possesses difficulty to decentralize and utilize renewable electricity. Plasma assisted catalysis seems to be a suitable alternative. Authors report a systematic investigation of ammonia synthesis using a rotating gliding arc (RGA) “warm” plasma, over Fe, Ni, and Cu catalysts in a post-plasma configuration that mitigates plasma-induced degradation. Under identical hydrodynamic conditions, performance of Fe (62.7 ppm) > Ni (54.0 ppm) > Cu (40.7 ppm), indicating the catalyst surface drives the performance. A multi manifold vibrational volcano model reveals that Fe has a “vibrational sweet spot” at moderate excitation (v ≈ 1–3), where vibrationally excited N₂ lowers the dissociation barrier without inducing desorption limitation, while Ni and Cu remains weakly bound; extension to extreme vibrational excitation (v≥10) predicts that with weaker binding metals becoming optimal once the dissociation barrier is fully cancelled. This preliminary investigation marks essential first step towards the use of non-equilibrium vibrational excitation to navigate the Sabatier landscape for sustainable nitrogen fixation.