Ammonia has garnered recognition as a zero-carbon fuel due to its high-density hydrogen storage capacity and its convenience for storage and transportation. To address the challenges associated with the direct usage of ammonia, the development of NH₃-to-H₂ conversion technologies has emerged as a promising and effective approach. Herein, we present for the first time that crystallized Sm₂O_3−x electrodes demonstrate high and stable electrocatalytic activities, including N₂ evolution rate and Faradaic efficiency, for ammonia electrolysis in a non-aqueous electrolyte. It was observed that Sm²⁺ ions in samarium oxide play an indispensable role in the ammonia electrooxidation reaction on the anodes. Furthermore, the mechanism of ammonia electrooxidation has also been elucidated, laying the foundation for a better understanding of the relationship between local structure and electrochemical properties in order to facilitate research on Pt-free electrocatalysts for the electrolysis of ammonia into H₂.