Pt and PtRu nanoparticles were prepared by NaBH 4 reduction in 1-n-butyl-3-methylimidazolium tetrafluoroborate and then directly incorporated in carbon aerogel. XRD measurements showed that both Pt and PtRu possess an FCC structure and most of the particles size is in the range 1-3 nm, as observed by TEM. The Pt and PtRu loaded carbon aerogel electrodes exhibited efficient O 2 reduction and methanol oxidation electrocatalysis, respectively. Nanosized materials have attracted extensive attention due to their unique physical and chemical properties. 1 Nanoparticles (NPs) of noble metals, in particular, have shown high catalytic capabilities for reactions of both scientific 2 and industrial importance. 3 The most common method employed for the preparation of metal NPs is the reduction of metal ions in aqueous solutions and if necessary, transferred to organic phases for specific purposes. 4 Ionic liquids (ILs) are ionic compounds with low melting points and unique solvents exhibiting unique properties such as low vapor pressure and chemical and electrochemical stability. 5 Therefore, they are very attractive media for many purposes including media for the preparation of metal nanoparticles (MNPs). 6 ILs can act as supports and stabilizers against agglomeration. 7 MNPs, such as Au NPs have been formed in ILs in the absence of stabilizing reagents and have been applied in electrochemical analysis. 8 Pt and Pt-Ru alloys are widely used as electrocatalysts in H 2 /air and direct methanol fuel cells, respectively. 9 A great deal of effort has been devoted to the synthesis of different nanostructured materials with the goal of improving their catalytic activity and reducing the noble metal quantity loaded on the electrode surface. Catalytic electrodes are usually prepared by deposition of the catalyst on high surface area carbon particles, such as Vulcan XC = 72. 10
Oxidation of methane at ambient conditions to useful oxygenates at a bilayer-coated electrode is demonstrated. The composition of the coating, a Mn porphyrin mediator layer on top of a N(OH)2/NiOOH...
The formation of Cu and Pt nanoparticles in an imidazolium-based ionic liquid was followed by UV-Visible spectroscopy. The different growth processes, autocatalytic first order and oriented second order, for Cu and Pt, respectively, is attributed to the different chemical nature of the metal particles surface. Stabilization through layering of the particles surface by the ionic liquid has an important impact on the use of noble and non-noble metal nanoparticles in energy conversion systems such as fuel cells and CO 2 electrocatalytic reduction to useful fuels. Nanoparticles (NPs) possess unique optical, thermal, electronic, and catalytic properties which strongly depend on their size, shape, and monodispersity. [1][2][3][4][5][6][7] As such, there is an increasing interest of comprehending the complex process by which NPs are generated. NPs generation includes nucleation and growth processes. LaMer investigated the formation of sulfur sols and suggested nucleation which can occur until a nucleus of critical size is obtained. 8,9 Further growth on the nucleus according to this mechanism is spontaneous but diffusion limited. Finke and coworkers have disputed LaMer mechanism and proposed a continuous nucleation slow process followed by a subsequent autocatalytic surface growth process. [10][11][12] Ostwald ripening is another coarsening mechanism in which larger nanocrystals grow at the expense of smaller ones and is driven by the higher solubility of small NPs. 13,14 Coalescence between particles, known also as aggregation growth, has recently been revealed to play an important role in the NPs growth.15-18 Some in situ analytical techniques, such as small angle X-ray scattering, 15 optical spectroscopy which has been applied for semiconductor NPs,19 and TEM 20 have been used to clarify the different processes involved in the generation of NPs.The stability of metal NPs relies mainly on the steric and/or electronic protection provided by different types of water or organic solvent soluble stabilizers such as surfactants, polymers, quaternary ammonium salts, and polyoxoanions. 21,22 It has been reported in this respect that ionic liquids (ILs) stabilize NPs without adding a surface ligand and by means of their interaction with metals which is exclusive to their components structure. [23][24][25] The ILs possess other unique properties such as low vapor pressure, wide liquidus range, highly ionic environment, wide electrochemical window and pre-organized structure.26 Thus, the synthesis of NPs in ILs is becoming a very active field of research 20,27-34 which has been reviewed in recent literature. [35][36][37][38][39] However, while the stability of NPs in ILs has been widely investigated, NPs growth mechanisms and kinetic aspects in these media are still not fully understood. Imidazolium-based ILs form extended hydrogen bonds and a π-π stacking network. They are consequently highly structured and are described as "supramolecular" fluids. 26,40,41 This structured organization favors well-defined and extended ordering...
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