Abstract: Developing low-cost, highly active, and durable electrocatalysts for the ammonia oxidation reaction (AOR) is pivotal for enhancing the overall efficiency of ammonia-to-hydrogen conversion technologies. In this work, a monolithic Ni-Cu-Mo electrocatalyst featuring a hierarchical nanoflower architecture was in-situ constructed on a nickel foam (NF) substrate which was both the support and nickel source via a facile one-step hydrothermal method. The integrated electrode was directly applied to ammonia-to-hydrogen production. Experimental results demonstrate that the Ni-Cu-Mo catalyst exhibits exceptional electrocatalytic activity, achieving a low onset potential of 1.32 V (vs. RHE)@10 mA·cm^-2. Furthermore, it maintains a stable current density exceeding 100 mA·cm^-2 for 64 h of continuous operation at 1.5 V (vs. RHE), showcasing outstanding potential for industrial applications. Mechanistic insights reveal that the morphology of hierarchical nanoflower induced by Mo-doping provides ample exposure of active sites, while the three-dimensional (3D) nickel foam scaffold ensures efficient charge transport and enhances mechanical and chemical stability during the electrolysis process. Simultaneously the electronic interaction between Ni and Cu significantly accelerate the AOR reaction kinetics. This study presents a novel self-supported Ni-Cu-Mo electrocatalyst as a robust material platform for efficient ammonia-based hydrogen production and provides innovative strategies for designing electrocatalytic systems for ammonia-hydrogen blended zero-carbon fuels in future.

Key words: ammonia oxidation, electrocatalysis, nanocomposites, ammonia-hydrogen blended zero-carbon fuel, long-term stability