Anode catalysts electrocatalytic activities

The electrocatalytic activity of the nanostructured Au and AuPt catalysts for MOR reaction is also investigated. The CV curve of Au/C catalysts for methanol oxidation (0.5 M) in alkaline electrolyte (0.5 M KOH) showed an increase in the anodic current at 0.30 V which indicating the oxidation of methanol by the Au catalyst. In terms of peak potentials, the catalytic activity is comparable with those observed for Au nanoparticles directly assembled on GC electrode after electrochemical activation.We note however that measurement of the carbon-supported gold nanoparticle catalyst did not reveal any significant electrocatalytic activity for MOR in acidic electrolyte. The... 

Platinum, ruthenium and PtRu alloy nanoparticles, prepared by vacuum pyrolysis using Pt(acac)2 and Ru(acac)3 as precursors, were applied as anode catalysts for direct methanol oxidation . The nanoparticles, uniformly dispersed on multiwaUed carbon nanotubes, were all less than 3.0 nm in size and had a very narrow size distribution. The nanocomposite catalysts showed strong electrocatalytic activity for methanol oxidation, which can... 

Will the electrocatalytic activity be maintained in spite of (a) catalyst poisoning phenomena, particularly on the anode side, and (b) catalyst agglomeration phenomena, particularly on the cathode ... 

Next, we examined the effects of control of the microstnicture such as pore-size distribution (or porosity) and the ohmic resistance of SDC layers on the improvement of the electrocatalytic activity of the SDC anode with and without nm-sized Ru metal catalyst loading. Fine polymer beads (cross-linked polystyrene, d = 1.2 pm) were added to the SDC paste, resulting in the fonnation of pm-sized pores after sintering, which can improve the gas-diffusion rates in the electrode. 

Materials effective as anode catalysts for epoxidation of 1-hexene by the method in Figure 2 were screened. Among various metal oxides, metal salts and metal blacks tested, the most active and selective anode catalyst for the formation of 1,2-epoxy hexane was Pt black (Table 1). The oxidation efficiency for the formation of epoxide defined by equation 9 was about 26% and its selectivity was 66%. Pt black samples obtained from different producers or prepared in this work showed quite low electrocatalytic activity. However, the calcination of these inactive Pt blacks in air at 673 K substantially enhanced the catalytic activities of these samples. XPS studies on various Pt black samples suggested that a Pt02 phase was associated with the active oxygen for the epoxidation. 

The successful choice of RuOx as a redox catalyst was prompted by the fact that RuOx anodes show high electrocatalytic activity (i. e. low overvoltage) for O2 evolution in the electrolysis of water. 

PANI-NTs synthesized by a template method on commercial carbon cloth have been used as the catalyst support for Pt particles for the electro-oxidation of methanol [501]. The Pt-incorporated PANl-NT electrode exhibited excellent catalytic activity and stabUity compared to 20 wt% Pt supported on VulcanXC 72R carbon and Pt supported on a conventional PANI electrode. The electrode fabrication used in this investigation is particularly attractive to adopt in solid polymer electrolyte-based fuel cells, which arc usually operated under methanol or hydrogen. The higher thermal stabUity of y-Mn02 nanoparticles-coated PANI-NFs on carbon electrodes and their activity in formic acid oxidation pomits the realization of Pt-free anodes for formic acid fuel cells [260]. The exceUent electrocatalytic activity of Pd/ PANI-NFs film has recently been confirmed in the electro-oxidation reactions of formic acid in acidic media, and ethanol/methanol in alkaline medium, making it a potential candidate for direct fuel cells in both acidic and alkaline media [502]. 

In addition to the proton conductivity of the electrolyte, the performance of a fuel cell is largely dependent on the electrocatalytic activity of the anodic and cathodic interface. This depends both on the structure of the gas-electrocatalyst-electrolyte three phase boimdaries and on the electrocatalytic activity of the charge transfer reaction that takes place along the electrochemical interface. The former case determines the extent of the electrochemical surface area (ESA), while the latter is directly related to the physicochemical properties of the Pt based catalyst and the extent to which its catalytic properties are affected by its contact /interaction with the polymer electrolyte. 

One possibility is the electrocatalytic preferential oxidation (cPrOx) (Zhang Datta, 2005), which is simply the electrochemical version of PrOx. By exploiting the strong selective CO adsorption on the anode Pt catalyst (Eqn (3.22)), coupled with the fact that H2O can be activated by the anode catalyst at certain electrode potentials to produce surface hydroxyl radicals, especially on Ru cocatalyst, the cPiOx process involves the following chemistry ... 

Since the discovery of carbon nanotubes in the early 1990s [273] there has been emerging interest in their applicability as catalyst supports for low-temperature PEMFCs. Recently, Lee et al. reviewed the area of Pt electrocatalyst preparation techniques using carbon nanotubes and nanofibers as supports [274]. Here, the emphasis will be on the impact of novel nanostructured carbon supports (ordered mesoporous materials, nanotubes, and nanofibers) on the electrocatalytic activity with respect to direct fuel cell anodes. 

Electrocatalysts advocated for methanol oxidation at the anode and oxygen reduction at the cathode in DMFCs are required to possess well-controlled structure, dispersion, and compositional homogeneity [46 9]. The electrocatalytic activities of both anode and cathode catalysts are generally dependent on numerous factors such as particle size and particle size distribution [50-54], morphology of the catalyst, catalyst composition and in particular its surface composition [55,56], oxidation state of Pt and second metal, and microstructure of the electrocatalysts [49,57,58]. With the frequently attempted surface manipulation strategies for nanosized electrocatalysts to increase their catalytic efficiencies toward MOR and ORR, rigorous characterization techniques which can provide information about nanoscale properties are critically required. For example, parameters such as particle size and variation in surface composition have strong influence on catalytic efficiency. Further, if the nanoparticles are comprised of two or more metals, both the composition and the actual distribution will... 

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