Composite electrocatalyst

Nallathambi V, Wu G, Subramanian NP, Ktunaragura SP, Lee JW, Popov BN (2007) Highly active carbon composite electrocatalysts for PEM fuel cells. ECS Trans 11 241-247... 

Snyder J, Fujita T, Chen MW, Erlebacher J (2010) Oxygen reduction in nanoporous metal-ionic liquid composite electrocatalysts. Nat Mater 9(11) 904—907... 

Chung HT, Won JH, Zelenay P (1922) Active and stable carbon nanotube/nanoparticle composite electrocatalyst for oxygen reduction. Nature Communications 4, doi 10.1038/ncomms2944... 

Figure 4.11. The effect of various binary anode catalyst formulations on DMFC polarization PtNi and Pt/macrocycles (Ni, Co, Mn, and Rh). Anode Pt load 0.4 mg cm 1 M CH3OH, 1 ml min cathode operated with dry O2 at atmospheric pressiure 368 K [87]. (With kind permission from Springer Science+Business Media Joimial of Applied Electtochemistry, Composite electrocatalysts for anodic methanol and methanol-reformate oxidation, 31, 2001, 811-17, Goetz M, Wendt H, figme 4.)...

Goetz M, Wendt H. Composite electrocatalysts for anodic methanol and methanol-reformate oxidation. J Appl Electrochem 2001 31 811-17. 

Thus, worldwide efforts have focused on the elucidation of the reaction mechanism. For this purpose, knowledge about the following items is vital (1) identification of reaction products and the electrode kinetics of the reactions involved, (2) identification of adsorbed intermediate species and their distribution on the electrode surface, and (3) dependence of the electrode kinetics of the intermediate steps in the overall and parasitic reactions on the structure and composition of the electrocatalyst. It is only after a better knowledge of the reaction mechanisms is obtained that it will be possible to propose modifications of the composition and/or structure of the electrocatalyst in order to significantly increase the rate of the reaction. 

Radmilovic V, Gasteiger HA, Ross PN. 1995. Structure and chemical composition of a supported Pt-Ru electrocatalyst for methanol oxidation. J Catal 154 98-106. 

Furthermore, the utilization of preformed films of polypyrrole functionalized by suitable monomeric ruthenium complexes allows the circumvention of problems due to the moderate stability of these complexes to aerial oxidation when free in solution. A similar CO/HCOO-selectivity with regards to the substitution of the V-pyrrole-bpy ligand by an electron-with-drawing group is retained in those composite materials.98 The related osmium-based redox-active polymer [Os°(bpy)(CO)2] was prepared, and is also an excellent electrocatalyst for the reduction of C02 in aqueous media.99 However, the selectivity toward CO vs. HCOO- production is lower. 

The elemental composition, oxidation state, and coordination environment of species on surfaces can be determined by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) techniques. Both techniques have a penetration depth of 5-20 atomic layers. Especially XPS is commonly used in characterization of electrocatalysts. One common example is the identification and quantification of surface functional groups such as nitrogen species found on carbon-based catalysts.26-29 Secondary Ion Mass spectrometry (SIMS) and Ion Scattering Spectroscopy are alternatives which are more surface sensitive. They can provide information about the surface composition as well as the chemical bonding information from molecular clusters and have been used in characterization of cathode electrodes.30,31 They can also be used for depth profiling purposes. The quantification of the information, however, is rather difficult.32... 

Constantinos G. Tsiafoulis et al. report the electrochemical behaviour of a composite film based on ferrocene intercalated V205.nH20 xerogel (FeCp2-VXG) with photocrosslinkable polyvinyl alcohol with styrylpyridinium residues (PVA-SbQ), in order to be used as an electrocatalyst and host protein platform to develop an amperometric biosensor. 

Carbon hybrids and composites as ORR electrocatalysts 14.3.3.1 Nitrogen-doped carbon... 

Fig. 3. Schematic illustration of the synthesis of metal nanoparticles within dendrimer templates. The composites are prepared by mixing of the dendrimer and metal ion, and subsequent chemical reduction. These materials can be immobilized on electrode surfaces where they serve as electrocatalysts or dissolved in essentially any solvent (after appropriate end-group functionalization) as homogeneous catalysts for hydrogenation and other reactions...

Figure 3. Schematic of fuel-cells electrodes design (a) metal electrode with two types of pores (b) composite electrode with dispersed electrocatalysts...

As a demanding reaction, it is very sensitive to the structural and compositional details of the anode materials. For this reason, research on anodes for O2 evolution calls for close characterization of electrocatalysts, especially from the point of view of materials chemistry and physics. 

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