Unraveling the Catalytic and Plasmonic Roles of g-C 3 N 4 Supported Ag and Au Nanoparticles Under Selective Photoexcitation

Herein, the photocatalytic roles of silver (Ag) and gold (Au) nanoparticles (NPs) on graphitic carbon nitride (CN) nanosheets are thoroughly investigated under UV (250–380 nm), UV–vis (256–600 nm), and green laser (532 nm). Under UV light, Ag and Au NPs capture photogenerated electrons from CN and function as cocatalysts. The dual roles of Ag and Au, as cocatalyst as well as a plasmonic photocatalyst, lead to reduced RhB degradation under UV–vis light. Band-gap excitation occurs in unison with surface plasmon resonance (SPR) under UV–vis light. The synchronicity leads to forward and back electron transfer at the metal–semiconductor junction, thus increasing interfacial carrier recombination. The plasmonic systems show the best result under visible light (532 nm). Plasmonic hot-electron injection from metal to CN triggers the SPR-driven photocatalysis. The photoconductivity current–voltage ( I – V ) measurement indicates enhanced free-carrier generation under white light (400–730 nm) as well as under selective excitations at 405, 470, and 530 nm. These freely available carriers actively participate in photocatalysis.