Large-scale synthesis and enhanced visible-light-driven photocatalytic performance of hierarchical Ag/AgCl nanocrystals derived from freeze-dried PVP–Ag+ hybrid precursors with porosity

• Hierarchical Ag/AgCl nanocrystals were synthesized via a freeze-drying route.
• The Ag/AgCl nanocrystals strongly absorb visible light in 400–800 nm.
• The enhancement in photocatalysis results from the high visible-light absorbance.
• The freeze-dried PVP–Ag+ hybrid plays a key role in forming hierarchical Ag/AgCl.
• The hierarchical structure is helpful to improve photocatalytic performance.

To achieve high-performance, hierarchical plasmonic Ag/AgCl photocatalysts, a freeze-drying route was developed to form porous PVP–Ag+ hybrid compounds, which were then transformed to hierarchical Ag/AgCl nanocrystals through a liquid–solid precipitation reaction followed by a partially photoreduction under ambient conditions. The PVP–Ag+ hybrid precursors and their final Ag/AgCl nanocrystals obtained were characterized by various techniques. The hierarchical Ag/AgCl nanocrystals obtained had an apparent size range of 156 ± 50 nm, and the surfaces of the large particles were covered with small nanocrystals with sizes of 33 ± 12 nm. The photocatalytic performance of the hierarchical Ag/AgCl nanocrystals was estimated by degradating organic dyes (i.e., RhB, MO, and MB) and alcohols (i.e., methanol and isopropanol) under visible light (λ ≥ 420 nm) and sunlight. The results indicated that the hierarchical Ag/AgCl nanocrystals obtained were efficient visible-light-driven photocatalysts in decomposing organic dyes, and their RhB photodegradation rates (∼0.97 min−1) was ∼54 times higher than that (∼0.018 min−1) of TiO2 (P25) nanocrystals under the same visible-light conditions. The photodegradation efficiency of methanol and isopropanol reached ∼45% and 35%, respectively, after visible-light irradiation for 60 min according to the COD data. The enhancement in visible-light-driven photodegradation performance results from the high absorbance through 350–800 nm due to the SPR effect of metal Ag species embedded in the hierarchical AgCl host nanocrystals. The influencing factors and possible growth mechanism of the Ag/AgCl nanocrystals were investigated, and the PVP molecules and the freeze-drying process were highly influenced the size and morphology of Ag/AgCl nanocrystals. The outstanding advantage of the freeze-drying assisted route is its ability in large-scale synthesis of hierarchical Ag/AgCl nanocrystals.

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