A Continuous-flow Photocatalytic Reactor for the Precisely Controlled Deposition of Metallic Nanoparticles

Summary

For a continuous and scalable synthesis of noble-metal-based nanocomposites, a novel photocatalytic reactor is developed and its structure, operation principles, and product quality optimization strategies are described.

Abstract

In this work, a novel photocatalytic reactor for the pulsed and controlled excitation of the photocatalyst and the precise deposition of metallic nanoparticles is developed. Guidelines for the replication of the reactor and its operation are provided in detail. Three different composite systems (Pt/graphene, Pt/TiO₂, and Au/TiO₂) with monodisperse and uniformly distributed particles are produced by this reactor, and the photodeposition mechanism, as well as the synthesis optimization strategy, are discussed. The synthesis methods and their technical aspects are described comprehensively. The role of the ultraviolet (UV) dose (in each excitation pulse) on the photodeposition process is investigated and the optimum values for each composite system are provided.

Introduction

Metallic nanoparticles, especially noble metals (e.g., Pt, Au, Pd) have vast applications in catalysis¹. In general, decreasing the size of the nanoparticles (NPs) increases their catalytic activity while maintaining the cost (weight) constant, but it also makes their application more difficult. NPs (usually smaller than 10 nm) have great tendencies to aggregation, which degrades their catalytic activity; however, immobilization on suitable substrates can mostly resolve this problem. Furthermore, depending on the application type (e.g., electrocatalysis), it is sometimes necessary to immobilize the NPs on conductive substrates^....

Protocol

1. Fabrication and operation of the photocatalytic deposition reactor

CAUTION: When UV lamps are turned on, use UV-C protective glasses.

1. Fabrication of the photocatalytic deposition reactor
   1. Cover the inner surface of a polyvinyl chloride (PVC) pipe (diameter x length = 15 cm x 55 cm; other materials can also be used) with a thick, polished, and adhesive-backed aluminum foil. Install five 55 W UV-C lamps (see Table of Materials) on the inner surface of the tube at equal distance.
   2. Fix a quartz tube (diameter x length = 0.5 cm x 55 cm) along the central axis of the PVC tube (....

Results

XPS is one of the most powerful techniques for confirming the formation of metallic NPs and study their chemical states. For this purpose, both survey spectra and high-resolution spectra (of Pt_4f and Au_4f) were recorded, which confirms the complete reduction of the metallic cations and successful deposition of the NNPs (Figure 3). For the deconvolution of both Pt_4f and Au_4f, initially, a Shirley background subtracti.......

Discussion

Nanoparticles are the most widely used form of noble-metal-based catalysts. In almost all cases, NNPs are deposited either on a conductive or a semiconductive support material. This hybridization is mostly done by the reduction of the cations of the noble metal in the presence of the intended substrate (material). Hence, a successful synthesis method for the production of NNP-based nanocomposite should meet at least two main requirements: 1) the reduction of the cations should be efficient and complete; 2) the deposition.......

Materials

Name	Company	Catalog Number	Comments
Chloroplatinic acid solution	Sigma Aldrich	262587-50ML
Hydrogen tetrachloroaurate(III) hydrate	Alfa Aesar	12325.03
TiO2 Nanopowder (TiO2, anatase, 99.9%, 100nm)	US research nanomaterials	US3411
Graphite powder	Alfa Aesar	10129
Sulfuric acid	Sigma Aldrich	1120802500
Hydrogen peroxide	Sigma Aldrich	H1009-100ML
L-Ascorbic acid	Sigma Aldrich	A92902-500G
Hydrochloric acid	Sigma Aldrich	320331-2.5L
Sodium hydroxide	Sigma Aldrich	S5881-1KG
Potassium permanganate	Merck	1050821000
Corning® Silicone Septa for GL45 Screw Cap	Sigma Aldrich (Corning)	CLS139545SS
Polyvinyl chloride pipe	Koctas		UV-Reactor casing
Fuded silica (Quartz) tube	Technical Glass Products
UV−C lamps	Philips	TUV PL-L 55W/4P HF 1CT/25