Site-Differentiated Self-Assembled PtMn Nanocluster Shells Enable Dual-Site Ammonia Oxidation in Direct Ammonia Fuel Cells

Direct ammonia fuel cells (DAFCs) represent a promising carbon-neutral energy conversion technology, yet their widespread application is significantly hindered by the sluggish kinetics of the ammonia oxidation reaction (AOR). To address this, atomically dispersed Mn within Pt nanoclusters that spontaneously self-assemble into continuous shell architectures on carbon black support are developed. Comprehensive characterization combined with theoretical calculations reveals a dual-site synergistic mechanism, wherein Mn sites serve as the primary centers for NH3 capture and dehydrogenation to *NH2 while Pt sites function as secondary active sites to adsorb additional *NH2 intermediates and facilitate subsequent N–N coupling reactions. The optimal catalyst achieves ideal intermediate binding satisfying Sabatier’s principle, delivering a peak current density of 22.69 mA cm–2 (9-fold enhancement over commercial PtIr/C). When integrated into a practical DAFC, the catalyst achieves a peak power density of 14.22 mW cm–2 at 60 °C, outperforming most reported systems.