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

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-CN nanosheets broadened the visible absorption range, reduced electron-hole recombination, and increased electronic communication at the interface. g-CN/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-CN alone. The H evolution of g-CN/Ag_CC (CC: ), g-CN/Ag_GT (GT: green tea), and g-CN/Ag_PP (PP: pomelo peels) reached 252.6, 125.3 and 92.0 μmol g at 180 min at the first cycle, respectively. Among them, g-CN/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-CN 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 H production under low-intensity visible-light irradiation.