Nanogap Engineered Plasmon‐Enhancement in Photocatalytic Solar Hydrogen Conversion

Graphitic carbon nitride modified with plasmonic Ag@SiO₂ core–shell nanoparticles (g‐C₃N₄/Ag@SiO₂) are proposed for enhanced photocatalytic solar hydrogen evolution under visible light. Nanosized gaps between the plasmonic Ag nanoparticles (NPs) and g‐C₃N₄ are created and precisely modulated to be 8, 12, 17, and 21 nm by coating SiO₂ shells on the Ag NPs. The optimized photocatalytic hydrogen production activity for g‐C₃N₄/Ag@SiO₂ is achieved with a nanogap of 12 nm (11.4 μmol h^?1) to be more than twice as high as that of pure g‐C₃N₄ (5.6 μmol h^?1). The plasmon resonance energy transfer (PRET) effect of Ag NPs is innovatively proved from a physical view on polymer semiconductors for photoredox catalysis. The PRET effect favors the charge carrier separation by inducing electron–hole pairs efficiently formed in the near‐surface region of g‐C₃N₄. Furthermore, via engineering the width of the nanogap, the PRET and energy‐loss Förster resonance energy transfer processes are perfectly balanced, resulting in considerable enhancement of photocatalytic hydrogen production activity over the g‐C₃N₄/Ag@SiO₂ plasmonic photocatalyst.