Balancing Local Oxophilicity on PtMo Alloys to Facilitate N–N Coupling for Enhanced Ammonia Electrooxidation in Direct Ammonia Fuel Cells

Abstract Low-temperature direct ammonia fuel cells (DAFCs) have attracted increasing attention as promising carbon-free power-generation devices, whereas their practical performance is still limited by the sluggish anodic ammonia oxidation reaction (AOR). Since AOR proceeds through hydroxide-assisted dehydrogenation of ammonia-derived intermediates followed by N–N coupling, its efficient operation depends on a catalyst surface that can sustain these sequential transformations. Herein, the local oxophilicity on PtMo alloys is compositionally balanced to facilitate N–N coupling during ammonia electrooxidation. Mo incorporation modulates the electronic structure of Pt and establishes a composition-dependent reaction environment, resulting in a distinct volcano-type dependence of AOR activity on Mo incorporation. In situ attenuated total reflectance Fourier transform infrared and Raman spectroscopies reveal enhanced NH3 consumption and earlier emergence as well as faster growth of the N2Hy-related signal on the optimal catalyst, indicating facilitated conversion of NHx species toward N–N coupling. Consequently, the optimized alloy delivers a peak current density of 21.19 mA cm–2, representing an over 10-fold enhancement over commercial PtIr/C. When integrated into a DAFC, it achieves a peak power density of 15.37 mW cm–2 at 80 °C. This work highlights balancing the local oxophilicity as an effective approach for regulating N–N coupling in Pt-based AOR electrocatalysts.