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.