Core-Shell PtIr Nanocubes with Lewis Acidic Ir Sites for Enhanced Ammonia Electrooxidation in Direct Ammonia Fuel Cells.

Direct ammonia fuel cells (DAFCs) represent a promising carbon-neutral energy technology, yet their practical application is severely hindered by the sluggish kinetics of the anodic ammonia oxidation reaction on traditional platinum-based catalysts. Herein, high-crystallinity PtIr nanocubes featuring a Pt-rich core/Ir-rich shell architecture are constructed by exploiting the differential reduction kinetics of the metal precursors. Spectroscopic analyses reveal oxygen-associated coordination and electron-deficient states around Ir, while pyridine-adsorbed Fourier transform infrared spectra establish surface Lewis acidity. Together, these findings support a role for Lewis acidic Ir sites in facilitating NH3 interaction and subsequent *NHx intermediate evolution. The catalyst delivers an exceptional mass activity of 151.45 A g-1, more than four times that of the commercial PtIr counterpart. Furthermore, a prototype DAFC equipped with this anode achieves a peak power density of 18.98 mW cm-2 at 60 °C, demonstrating efficient translation to device-level performance.