Single-nanoparticle-thick three-phase plasmonic catalysis for efficient nitrogen photofixation without sacrificial agents

Plasmonic catalysis promises efficient green ammonia production from nitrogen gas, water, and (sun)light. However, existing designs are limited by poor catalytic performance and reliance on organic sacrificial agents. Here, we achieve efficient ammonia photosynthesis at ambient conditions without sacrificial agent by introducing a single-particle-thick plasmonic superlattice at a three-phase catalytic interface. By organizing Ag-square superlattice on a hydrogel to create an electromagnetically hot solid-liquid-gas tri-interface, our three-phase plasmonic catalyst achieves a superior ammonia formation rate of 101 µmol h⁻¹ g⁻¹, surpassing conventional two-phase configuration by ∼33-fold. More importantly, our unique design attains up to ∼26-fold and ∼2500-fold enhancements in ammonia formation rate and apparent quantum yield, respectively. Mechanistic investigations uncover the importance of three-phase plasmonic interface to efficiently concentrate light and enrich immiscible gas-liquid reactants at point-of-catalysis, thereby boosting nitrogen photofixation. Our work offers valuable insights for designing multifunctional plasmonic ensembles towards sustainable chemical manufacturing and a carbon-free hydrogen economy.