Surface-Enhanced Raman Spectroscopic Study of Key Intermediates in Electrochemical Ammonia Decomposition

Ammonia is an alternative hydrogen storage material and a promising source of sustainable clean energy. The lack of a mechanistic understanding of ammonia electrooxidation hinders the efforts to overcome the slow kinetics of the anode reaction in direct ammonia fuel cells. Herein, we use surface-enhanced Raman spectroscopy to study the electro-decomposition of ammonia on the Au surface. We observe three key reaction intermediate species of *NH₂, *NH and *NNH and thereby disclose a multistage interfacial decomposition mechanism. Among the three, detection of the N-coupled species fills the blank in the mechanistic study of ammonia oxidation. Additionally, we investigated the influence of the reactant concentrations on the different oxidation stages. This spectroscopic evidence opens up promising avenues to overcome the limitations associated with ammonia fuel cells.