Competitive reactivity determines size- and composition-focusing and optimized catalytic performance in multi-domain multimetallic nanocrystals

Multimetallic nanocrystals (NCs) offer unique properties driven by synergistic interactions among their constituent metals. While colloidal chemistry enables control over size and composition, competing reactivities among metal precursors often complicate the synthesis of complex NCs. Here, we systematically elucidate how the competitive reactivity of different metals in solution can be exploited to synthesize uniform pentametallic NCs despite numerous competing pathways. Mechanistic studies reveal heterodimers as key intermediates that mediate further metal incorporation via selective nucleation. Remarkably, the addition of more metals suppresses homogeneous nucleation, resulting in size- and composition-focusing to produce complex NCs with distinct multimetallic domains. When supported, these NCs show excellent thermal stability and catalytic activity for ammonia decomposition, offering a promising strategy for designing complex nanomaterials for energy-related applications.