Abstract: The ammonia oxidation reaction (AOR) is a key process for establishing ammonia as a practical hydrogen carrier, thereby enabling sustainable hydrogen storage and transportation. However, platinum (Pt)-based nanocrystals (NCs) typically suffer from rapid deactivation due to the strong adsorption of nitrogen species, which severely limits their catalytic performance. Here, we report PtCu-polyaniline core-shell (PtCu@PANI) NCs, in which the PANI shell thickness is precisely controlled to optimise electron transfer and mitigate nitrogen poisoning. The π-conjugated structure of PANI and its interfacial coupling with PtCu facilitate charge transport, weaken the adsorption strength of nitrogen-containing intermediates, and lower the energy barrier of the rate-determining step, thereby enhancing AOR kinetics. The PtCu@PANI NCs deliver a remarkable mass activity of 232.85 A g^-1, nearly one order of magnitude higher than commercial Pt/C and surpassing most reported AOR catalysts. In addition, the robust PANI shell provides effective protection against corrosive environments, affording excellent long-term durability. This study demonstrates a rational core-shell NC design, in which precise tuning of the core-shell interplay yields both superior catalytic activity and durability, offering a promising strategy for efficient and durable ammonia electrolysis.

Key words: Ammonia oxidation reaction, Polymer shell, PtCu alloy, Interface engineering