Eco-synthesis of green silver nanoparticles using natural extracts and its application as co-catalyst in photocatalytic hydrogen production

Abstract

Green silver nanoparticles (AgNPs) were synthesized using natural extracts as reducing agents and were firstly applied as co-catalysts in low-intensity-visible-light driven photocatalytic hydrogen production (PH2P), which a solution for green energy sources and independence from fossil fuels. The as-prepared AgNPs possessed size in a few tens nanometers and exhibited surface plasmon resonance (SPR) effects in the 310–560 nm region. Depositing AgNPs on g-C₃N₄ nanosheets broadened the visible absorption range, reduced electron–hole recombination, and increased electronic communication at the interface. g-C₃N₄/Ag demonstrated high PH2P efficiency, stability over three consecutive cycles, and a rapidly rising photocurrent under low-intensity visible light irradiation, although these features were not observed in g-C₃N₄ alone. The H₂ evolution of g-C₃N₄/Ag_CC (CC: Cinnamomum camphora), g-C₃N₄/Ag_GT (GT: green tea), and g-C₃N₄/Ag_PP (PP: pomelo peels) reached 252.6, 125.3 and 92.0 μmol g⁻¹ at 180 min at the first cycle, respectively. Among them, g-C₃N₄/Ag_CC showed the highest photocatalytic activity, which may be attributed to the superior morphology, optical properties of AgNPs_CC, and efficient electron transfer from g-C₃N₄ to AgNPs_CC. The SPR effect and Schottky barriers formed at the interface could contribute to enhancing the overall efficiency of the heterojunction photocatalysts. The results highlighted a crucial advancement toward H₂ production under low-intensity visible-light irradiation.