Electrochemical Synthesis of Continuous Controllable Ag Nanoparticles from Quaternary Ionic Liquid Microemulsions and Electrocatalytic Activity

Abstract

The synthesis of metal nanoparticles (NPs) with controllable size from aqueous or organic solutions has long been a scientific and technological challenge. Here we show a unique electrodeposition approach from ionic liquid microemulsions (ILM) which enables simultaneous fabrication of uniform controllable Ag NPs at both electrode substrate and in bulk solution. In the ILM system containing cetyltrimethylammonium bromide (CTAB), butanol, 1-butyl-3-methyl-imidazolium chloride ([BMIM][Cl]), and an aqueous solution of silver nitrate, uniform Ag NPs with a narrow size distribution of 20∼50 nm could be electrodeposited on the cathode surface at low deposition current (0.2∼1.5 mA · cm −2 ). The size and size distribution of Ag NPs can be adjusted by tuning the deposition current, time, temperature and IL concentrations. Remarkably, at high deposition current (>1.50 mA · cm −2 ), the electrochemical reduction of Ag NPs takes place not only on the electrode surface, but also beyond into the bulk microemulsion phase. Uniform Ag NPs of diameters 2∼13 nm thus can be obtained from the bulk ILMs. It is found that the ionic liquid plays a quaternary role as a soft template and co-surfactant for the formation of micro-reactors, an electrolyte for enhancing conductivity, and an electron carrier facilitating electron transport between nanodroplets for Ag reduction. The electrocatalytic activity of the electrodeposited Ag NPs has been investigated for oxidation of glycerol for potential applications in direct alcohol fuel cells.Metal nanoparticles (NPs) have been extensively investigated for application in catalysis, electrocatalytic, logical labeling, photonics, and optoelectronics, owing to their unique set of mechanical, optical, electronic, and magnetic properties. 1,2 Enormous efforts have been devoted to preparing NP without agglomeration. 3-5 The use of microemulsions has received significant attentions in nanoparticle synthesis. 6-10 The microemulsion system can be used as microreactors to limit the nucleation, growth and agglomeration of NPs. 11 NPs with controllable size, narrow size distribution, and chemical composition could be obtained in such a medium through modulating the synthesis conditions. Electrodeposition 12,13 is also a powerful approach for preparation of nanoparticles which enables precise control of the nucleation and growth processes, and the purity, structure and morphologies of the crystals, and often operates under ambient and benign conditions. 14,15 However, direct electrodeposition in microemulsions is restricted owing to the large dielectric components and low conductivity in the microemulsions.Ionic liquids (ILs) had been used as solvent to prepare the metals and alloy by chemistry, plasma, electrochemistry, and electrodeposition. [16][17][18][19][20] Recently, ILs have been applied to substitute water or oil to form novel microemulsions in the presence of surfactants. The novel ionic liquid microemulsions (ILM) introduce several significant advantages, compared to conventional microemulsions, 21...

Synthesis of Silver Nanoparticles using Pulse Electrolysis in 1-n-butyl-3-methylimidazolium Chloride Ionic Liquid

“…This kind of ionic liquid was first utilized for the electrodeposition of silver by combining aluminum chloride in the form of mixed room temperature molten salts [26]. Silver nanoparticles were electrochemically prepared in a quaternary ionic liquid microemulsion system including [C4mim]Cl [27,28].…”

Demonstration of Feasibility Using Ionic Liquid as Electrolyte for Electrochemical Deposition and Recovery of Silver from Silver Oxide

“…20 Numerous ILs have been used for the electrodeposition of silver. 11,[21][22][23][24][25][26][27][28][29][30][31][32][33] However, various silver salts such as AgNO₃, AgCl, AgBF₄ and etc. instead of silver oxide were used as the silver sources, which shows that the IL [Hbet][TFSA] may be superior on Ag recovery from Ag₂O coin batteries.…”