Prominence of Cu in a plasmonic Cu–Ag alloy decorated SiO2@S-doped C3N4 core–shell nanostructured photocatalyst towards enhanced visible light activity

Abstract

A series of Cu–Ag bimetal alloys decorated on SiO₂ and the fabrication of few-layer S-doped graphitic carbon nitride (SC) warped over it to form a core–shell nanostructured morphology have been demonstrated and well characterized through various physiochemical techniques. HRTEM data confirmed the formation of a compact nanojunction between the SiO₂ and SC, where Cu–Ag is embedded uniformly with an average particle size of 1.3 nm. The Ag : Cu (1 : 3) between SiO₂ and SC produces 1730 μmol h⁻¹ g⁻¹ of H₂ under visible light illumination. Moreover, 6.2-fold current enhancement in the case of Ag : Cu (1 : 3) as compared to the Ag-loaded core–shell nanostructured photocatalyst indicates higher electron–hole-pair separation. The excellent activity was due to the synergistic alloying and plasmonic effect of Ag and Cu. DFT studies reveal that the Cu atom in the Cu–Ag bimetal alloy plays a pivotal role in the generation of H₂, and the reaction proceeds via a 4-membered transition state. The mechanistic insight proceeds from the generation of hot electrons due to the LSPR effect and their transfer to the SC layer via a compact nanojunction.