Plasmonic Coupling within Atomically Precise Nanocluster Dimers for Engineering Hot-Carrier Generation and Molecular Activation

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Activating the exceptionally strong N≡N bond remains a fundamental challenge due to the chemical inertness of molecular nitrogen (N2). Plasmonic nanoclusters offer a promising approach by generating localized electromagnetic fields and energetic hot carriers that can drive bond activation under ambient conditions. Here, we combine real-time time-dependent density functional theory with Ehrenfest molecular dynamics to reveal how plasmonic coupling between tetrahedral Ag20 nanoclusters governs N2 activation and dissociation. Systematic variation of the intercluster separation shows that a 6 Å nanogap maximizes near-field enhancement and hot-electron transfer to the adsorbed N2, accompanied by N–N activation. Consequently, N2 dissociation is achieved at incident field strengths as low as 0.5 V Å–1, whereas larger-gap dimers exhibit substantially lower activity. Similarly, isolated N2 remains intact under comparable conditions. These findings establish nanogap engineering as an effective strategy for optimizing plasmon-driven N2 activation and provide design principles for developing efficient plasmonic catalysts.