A facile and green approach was developed to in-situ prepare Ag nanoparticles (AgNPs) on the TiO₂. Through the (3-mercaptopropyl)trimethoxysilane (MPTMS), mono-dispersed AgNPs were loaded on TiO₂ (AgNPs@MPTMS-TiO₂). In the presence of NaBH₄, the AgNPs@MPTMS-TiO₂ displayed an ultra-high catalytic activity for 4-nitrophenol reduction, of which the apparent kinetic rate constant (k_app) reached up to 394 × 10^–3 s⁻¹. Comparing to the best previous performance (k_app = 120 × 10^–3 s⁻¹), the obtained Ag-catalysts made a huge progress. Moreover, the catalytic activity of the AgNPs@MPTMS-TiO₂ could be optimized via changing series of fabrication parameters including Ag⁺ precursor amount and MPTMS amount, and reaction time. Various characterization techniques including TEM, HRTEM, XPS, FT-IR and Zeta potential have been utilized to study the material morphology, valance states and surface chemistry. It revealed that the AgNPs were coordinated by MPTMS though R-S–Ag bonds, which could prohibit the AgNPs from self-aggregation. In addition, the R-S–Ag bonds favored reaction of AgNPs with BH₄⁻ and thus releasing substantial protons. Consequently, the increasing proton concentration would speed up the transformation from 4-hydroxylaminophenol to 4-aminophenol.

Graphic Abstract

In-situ grow Ag nanoparticles (AgNPs) on (3-mercaptopropyl)trimethoxysilane (MPTMS) modified TiO₂ with characters of small size, good distribution and controllable loading. The apparent kinetic rate constant (k_app) reaches as high as 394 × 10^–3 s⁻¹.

中文翻译：

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在 TiO2 上原位制备银纳米颗粒，以实现前所未有的 4-硝基苯酚还原高催化活性

开发了一种简便且绿色的方法来在 TiO ₂上原位制备 Ag 纳米粒子 (AgNPs) 。通过（3-巯基丙基）三甲氧基硅烷（MPTMS），将单分散的AgNPs负载在TiO ₂（AgNPs@MPTMS-TiO ₂）上。在NaBH ₄存在下，AgNPs@MPTMS-TiO ₂表现出超高的4-硝基苯酚还原催化活性，其表观动力学速率常数（k _app）达到394 × 10 ^–3  s ^-1。与之前的最佳性能（k _app  = 120 × 10 ^–3  s ⁻¹)，获得的银催化剂取得了巨大的进步。此外，AgNPs@MPTMS-TiO ₂的催化活性可以通过改变包括Ag ⁺前体量和MPTMS 量在内的一系列制造参数以及反应时间来优化。包括 TEM、HRTEM、XPS、FT-IR 和 Zeta 电位在内的各种表征技术已被用于研究材料形态、价态和表面化学。结果表明，AgNPs 是由 MPTMS 通过 RS-Ag 键协调的，这可以阻止 AgNPs 的自聚集。此外，RS-Ag 键有利于 AgNPs 与 BH _{4 的}反应^-从而释放大量质子。因此，增加质子浓度将加速从 4-羟基氨基苯酚到 4-氨基苯酚的转化。

图形摘要

在（3-巯基丙基）三甲氧基硅烷（MPTMS）改性的TiO ₂上原位生长Ag纳米颗粒（AgNPs），具有尺寸小、分布好和负载可控的特点。表观动力学速率常数 ( k _app ) 高达 394 × 10 ^–3  s ^-1。