Colloidal electrocatalytic properties

Multipods and Dendritic Nanoparticles of Platinum Colloidal Synthesis and Electrocatalytic Property... 

More recently Bouzek et al. investigated the effect of the preparation conditions of Pt-modified polypyrrole films on their electrocatalytic properties for the HOR [26]. Three methods were considered (1) cathodic deposition of Pt from H2PtCl6 in the previously synthesized film, (2) incorporation of colloidal Pt particles during the electropolymerization of polypyrrole (3) incorporation of [PtCU] as a counter-ion during the electropolymerization process and its subsequent reduction. Only the first two methods lead to active electrocatalytic films, whereas the last one gives very poor catalysts, maybe because the Pt particles are embedded in the PPy structure and therefore are not accessible to the reactant. 

Here, we give an example where the electrochemical and electrocatalytic properties of nanostructured Pt catalysts supported on glassy carbon, prepared with colloidal lithography, were tested with oxidation of preadsorbed CO, so-called CO-stripping, as a test reaction [99]. The Pt nanoparticles were prepared as described in Fig. 4.11, except that the polystyrene particles were removed by UV-ozone treatment. The particles had an average diameter of 122 11 nm and were about 40 nm high. There was no indication (by AFM... 

Many types of bimetallic catalysts have been used to investigate electrocatalytic performance, including single-crystal surfaces [6], sputtered particles [5,7], carbon-supported catalysts fabricated by impregnation reduction, and colloidal nanocrystals (NCs). Bimetallic single crystals are indispensable when investigating facet-specific electrocatalytic properties sputtered bimetallic particles can be used as model catalysts with a clean surface to study the effect of composition on... 

Multipods and dendritic nanoparticles of platinum colloidal synthesis and electrocatalytic property, in Metal Nanoclusters in Catalysis and Materials Science The Issue of Size Control. Part II Methodologies (eds B. Corain, G. 

Au Pt nanoparticles prepared by one-phase protocol and their electrocatalytic properties for methanol oxidation, L. Yang, J. Chen, X. Zhong, et al.. Colloids and Surfaces A Physicochem. Eng. Aspects, 2007, 295, 21. 

A preparation and characterization of new PtRu alloy colloids that are suitable as precursors for fuel-cell catalysts have been reported [43cj. This new method uses an organometallic compound both for reduction and as colloid stabilizer leading to a Pt/Ru colloid with lipophilic surfactant stabilizers that can easily be modified to demonstrate hydrophilic properties. The surfactant shell is removed prior to electrochemical measurements by reactive annealing in O2 and H2. This colloid was found to have nearly identical electrocatalytic activity to several other recently developed Pt/Ru colloids as well as commercially available Pt/Ru catalysts. This demonstrates the potential for the development of colloid precursors for bimetallic catalysts especially when considering the ease of manipulating the alloy composition when using these methods. 

Quite promising may be the study of photoelectrochemical properties of microheterogeneous semiconductor systems (porous electrodes, suspensions of different degrees of dispersion up to colloidal solutions), in which photosensitivity inherent in semiconductors is combined with high electrocatalytic activity typical of systems with a developed surface. 

Conclusions All three 30wt% PtsoRuso/Vulcan XC 72 electrocatalysts (Catl-3) generated by the respective reduction agents via the colloidal precursor route showed good electrocatalytic activity in methanol oxidation. Small differences in the surface structures, which are a direct consequence of the synthetic methodology used, is likely the reason for the differences in their electrochemical properties. 

Water is the active medium of PEFCs. From a chemical point of view, water is the main product of the fuel cell reaction. It is the only product in hydrogen fuel cells. Cells supplied with direct methanol or ethanol as the fuel produce water and carbon dioxide in stoichiometric amounts. The low operating temperature implies that water is present in liquid form. It mediates direct electrostatic as well as colloidal interactions in solutions or ink mixtures containing ionomeric, electronic, and electrocatalytic materials. These interactions control phase separation and structural relaxation phenomena that lead to the formation of PEMs and CLs. Variations in water content and distribution, thus, lead to transformations in stable structures of these media, which incur modifications in their physicochemical properties. It is evident that many of the issues of understanding the structure and function of fuel cell components under operation are intimately linked to water fluxes and distribution. 

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