Local Atom Disorder Mediated Crystal Facet Valence State of PtCu Alloy for Ultrafast Ammonia Oxidation Dehydrogenation

The Pt (100) facet of platinum-based alloys exhibits high potential in ammonia oxidation reaction (AOR) but is still a huge bottleneck in activity enhancement due to the sluggish NH_x-dehydrogenation kinetics. Herein, a local-disordered PtCu alloy (d-PtCu), with an increasing low-valence-platinum ratio on the (100) facet, is engineered to atomically boost AOR dehydrogenation behavior. Both in situ experimental and computational results demonstrate that substituting Pt atoms with Cu induces the formation of low-valence Pt^δ− sites and strongly oxidized Cu^δ+ species on the (100) facet for electronic redistribution. Benefiting from such enriched low-valence-platinum sites, d-PtCu/C possesses the strong asymmetric gradient orbital coupling between Pt_5d, Cu_3d, and NH₂ intermediates, and ultrafast NH₂ dehydrogenation at heteroatomic PtCu sites. As a result, at 0.64 V (vs RHE), the d-PtCu/C catalyst achieves a peak AOR current density of 294.4 A g_Pt⁻¹, which is 1.7 and 1.9-fold higher than those of ordered PtCu/C (169.9 A g_Pt⁻¹) and Pt/C (158.9 A g_Pt⁻¹), respectively. Notably, DAFCs equipped with this electrocatalyst demonstrate a record high peak power density per gram of Pt metal (122 mW mg_Pt⁻¹) at 40 °C. This work unveils a comprehensive atomic mechanism of introducing local disorder in alloys based on valence state engineering for developing efficient AOR electrocatalysts.