(317f) Ultrasonic-Assisted Synthesis of Photoresponsive Silver Supported Nanoparticles in Continuous Flow

Graphitic carbon nitride (g-C₃N₄) photocatalyst, which is a novel metal-free polymer semiconductor with a band gap of about 2.7eV, has attracted growing attention in the photocatalyst for H₂ production. The unique electronic structure with Ï€-conjugated graphitic provides special properties such as high stability and a visible light response. However, the low surface area and high recombination rate of photogenerated electron-hole pairs are still the barriers hindering the application of g-C₃N₄. Many strategies have been employed to increase the photocalytic activity. Among these methods, coupling with noble metal nanoparticles with surface plasmon resonance effect is a promising method. However, the coalescence and agglomeration of nanoparticles are great challenges for controlling particle size. Supported nanoparticles with small mean sizes can greatly improve the catalytic performance. Recently, size controlled supported nanoparticles have been synthesized continuously through microreactors. However, the inevitable use of organic steric capping agents hinders catalytic activity. Ultrasound, which can support cavitation and facilitate the disruption of particle agglomerates, is considered as an effective method for synthesis of small monodisperse nanoparticles.

Here in, we present a novel approach for ultrasonic-assisted continuous synthesis of Ag/g-C₃N₄ catalysts in the absence of organic steric capping agents. Supported nanoparticles were synthesized through mixing the support and reactants in a coiled flow inverter microreactor. Ultrasonic irradiation was applied in the nucleation and growth of nanoparticles in the microreactor. The synthesized Ag/g-C₃N₄ was characterized by TEM, ICP and PL techniques. The increase of ultrasonic power produces nanoparticles with smaller mean sizes, and the loading contents and photoelectron transfer performance of the supported catalyst are also affected. The catalytic performance of Ag/g-C₃N₄ was tested based on hydrogen-production from triethanolamine under visible light irradiation. The photocatalytic production H₂ rate with 5 wt% Ag/g-C₃N₄ prepared at an ultrasonic output of 60 W and at a residence time of 35 s was about 2.4 times as that of pure g-C₃N₄, respectively. This study not only provides a further understanding of the effect of the size of the supported catalyst on the performance, but also proposes an innovative method of continuous synthesis of the supported nanomaterials without organic steric capping agents, which provides a reference for the application of ultrasonic technology for industrial-scale production.

Reference:

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