Continuously Controllable Nano-silver, Palladium And Its Catalytic Activity In Electrodeposited Size Of Quaternary Ionic Liquid Microemulsion

The reducing of nanomaterials agglomeration in the synthesis process may be helpful to obtain uniform size and good dispersion nanomaterials. The ionic liquid containing both hydrophilic group and hydrophobic group is used as the co-surfactant, butanol is used as oil, cetyl-trimethylammonium bromide (CTAB) and cetyl-trimethylammonium chlorine (CTAC) are used as surfactant, aqueous solution of silver nitrate is the solution phase, the typical quaternary ionic liquid microemulsions(ILM) for electrocatalytic applications are made. The size and size distribution of Ag NPs can be adjusted by tuning the deposition current, time, temperature and ionic liquid concentrations. The electrocatalytic activity of the electrodeposited Ag NPs has been investigated for oxidation of glycerol.1. A lot of experiments performed to obtain the stable ILM, which the oil and surfactant phase concentration can change in a large range. Cyclic voltammetry(CV) shows that the scanning speed increased to 50 mV·s-1, ILM anodic stripping peaks of ILM disappeare indicating that Ag NPs reduction occurs not only on the electrode surface of the substrate but also occurs in ILM. Chronoamperometry(CA) and nucleation curve shows that the adding ionic liquids regulates the nucleation mechanism of Ag NPs. Linear sweep voltammetry(LS V) results show that a reduction peak potential of silver with the greater concentration of ionic liquid and a positive shift, shows that the addition of ionic liquids is in favor of silver reduction.2. The 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). at high deposition current (1.50-4.0 mA·cm-2) the electrochemical reduction of Ag NPs takes place not only on the electrode surface for small density but also beyond into the bulk microemulsion phase(2-13 nm). 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 for Ag reduction.3. The impacts of current density, deposition time, temperature, ionic liquid concentration on the size and morphology of Ag NPs electrodeposition on the electrode substrate. Electrodeposition results show that with the current density increase in the range of 0.20-1.50 mA·cm-2, Ag NPs size and density of nuclei deposited on the electrode substrate has increased; Ionic liquid concentration (wt% is mass ratio of microemulsion system) in the range of 1.5-6.6 wt%, the size of Ag NPs first decrease. The suitable electrodeposition conditions are obtained, the current density is 1.50 mA·cm-2, deposition time is 120s, the temperature is 298K, ionic liquid concentration is 5.5 wt%, Ag NPs with 20 nm can be got at these conditions.4. The effects of deposition current density, surfactant and ionic liquids concentration on the size and size distribution of Ag NPs electrodeposition from the bulk ILM (micelles) are studied. Electrodeposition results show that current density is in the range form 1.5-4.0 mA·cm-2, the ionic liquid concentration is in 1.5-7.7wt%, concentration of surfactant is 6.8-18.9 wt%, uniform and good distribution Ag NPs(2-11 nm) could be got. This indicates that the ionic liquids concentration for the effect of Ag NPs size is far greater than the surfactant. It is also suggests that ionic liquid can help to decrease the size of cell and play the important role as co-surfactants.5. In order to study the influence of Ag NPs size on the catalytic activity, glassy carbon electrode are modified with various sizes Ag NPs for the catalytic of glycerol.The results clearly indicated the size dependent electrocatalytic activity of Ag NPs for glycerol oxidation, and small size of Ag NPs is favorable for high catalytic activity owing to high specific surface area. Similar behavior is observed for Ag NPs deposited from the bulk phase of ILM under large current densities.6. The above ionic liquid microemulsions were improved, the lower viscosity and higher electrical conductivity 1-ethyl-3-methylimidazolium bisimidetriflate salt was selected as the co-surfactant, thus, a quaternary ionic liquid microemulsion (representatived by ILM) were built. Cyclic voltammetry results show that Pd NPs reduction process is a diffusion-controlled process. The size and density of Pd NPs can be tuned by varying the deposition current density and the ionic liquid content. Electrodeposition results show that ionic liquid content change in 2.01-10.07 wt% and the current density change in 0.02-0.40 mA·cm-2, uniform Pd NPs could be got. The suitable electrodeposition conditions are obtained, the current density is 0.20 mA·cm-2, deposition time is 120s, ionic liquid concentration is 6.04wt%, Pd NPs with 20 nm can be got at these conditions.7. In order to study effect of electrocatalytic reduction of oxygen(ORR) as the different sizes of Pd NPs, diversed Pd NPs used to modify a Pt electrode. CV of ORR show that the reduction peak current density increase with the size of Pd NPs decrease, integrating area increases increase 10 times owing to high specific surface area of small Pd NPs. The rotating disk electrode modified by Pd NPs used in ORR, cathodic polarization curves and Koutecky-Levich calculating illustrates the ORR on electrode modified Pd NPs is 2e-.