Pt-based nanoparticles

Different methods have been developed to prepare Pt-based nanoparticles supported on carbon powders (particularly Vulcan XC-72R). 

These pioneering results on smooth platinum obtained by EMIRS were confirmed by the new IR Reflectance Spectroscopy developed by Pons et al. (SNIFTIRS) and Weaver et al. (SPAIRS), able to observe intermediate species produced on carbon (e.g. Vulcan XC-72) supported Pt-based nanoparticles. 

We have reviewed the family of dealloyed Pt-based nanoparticle electrocatalysts for the electroreduction of oxygen at PEMFC cathodes, which were synthesized by selective dissolution of less-noble atoms from Pt alloy nanoparticle precursors. The dealloyed PtCua catalyst showed a promising improvement factor of 4-6 times on the Pt-mass ORR activity compared to a state-of-the-art Pt catalyst. The highly active dealloyed Pt catalysts can be implemented inside a realistic MEA of PEMFCs, where an in situ voltammetric dealloying procedure was used to constructed catalytically active nanoparticles. The core-shell structural character of the dealloyed nanoparticles was cmifirmed by advanced STEM and elemental line profile analysis. The lattice-contracted transition-metal-rich core resulted in a compressive lattice strain in the Pt-rich shell, which, in turn, favorably modified the chemisorption energies and resulted in improved ORR kinetics. 

Scheme 11.9 Loading of the ROMP-derived monolithic supports with Pt-based nanoparticles for continuous hydrosilylation reactions.

For example, our group developed a ROMP-based synthesis for these types of materials [68-74, 92-99] and described the use of these supports in heterogeneous catalysis [45, 98]. Since that time, numerous reviews have expounded the twenty-first century advancements in monolithic supports for separation science, heterogeneous catalysis, and tissue engineering [1, 100-114]. The published research from 2012 also includes the development of large-volume monolithic supports for biomolecule chromatography [115], boronate affinity chromatography columns [116], and monolith-supported Pt-based nanoparticles for hydrosilylation reactions [74]. 

The colloidal synthesis method has also been successfirlly tailored to allow for particle size and composition control, as well as shape control for Pt-based nanoparticles. Control of these factors will be discussed in Section 9.3. 

Electrochemical deposition has been used to deposit Pt and Pt-based nanoparticles on a wide variety of substrates, including glassy carbon [33], highly ordered pyrolytic graphite (HOPG) [34, 35], carbon black inside Nafion [36], carbon nanotubes [37], and PAN-based carbon fibers [38]. A number of papers also... 

The catalysts of choice for PEM fuel cells are Pt-based nanoparticles supported on high surface area carbons. In recent years the main research effort was in the improvement of catalytic activity for the oxygen reduction reaction (ORR) at the cathode. It is now demonstrated by a wealth of experimental and theoretical investigations, that the reaction rate for the ORR can be considerably increased by... 

This chapter is organized as follows after a short introduction on the type of carbon materials used in PEMFCs (Section 14.2), their physico-chemical properties will be discussed (Section 14.3). Section 14.4 will highlight the preparation of carbon-supported Pt-based nanoparticles, while Section 14.5 will discuss new strategies employed to design lowered-Pt-mass CLs. Finally, Section 14.6 will give conclusions and an outlook. 

To use Pt to the best extent, perfect CLs must achieve ionic (connection with the PEM), electronic (connection with the bipolar plate (BP)), and transport percolation (connection with the gas flow channels of the BP), the last two functions being ensured by the carbon materials used in the MEA and in the GDL. The carbon support shall also enable easy/homogeneous deposition and prevent agglomeration of the Pt-based nanoparticles. Therefore, its physicochemical and textural properties are key elements to the cell performance [2,3]. 

There is an exhaustive literature dealing with the synthesis of carbon-supported Pt-based nanoparticles (see, e.g.. Refs. [51-53] and references therein), but only a brief review of the most relevant elaboration techniques will be given here. The preparation of metal nanopartides is... 

Dissociative Adsorption of Ethanol and Acetaldehyde on Pt-Based Nanoparticle Catalysts... 

To completely oxidize ethanol to CO2, the dissociative adsorption of ethanol is the first key process, and thus has been studied for over 20 years [31,34,79-82]. In this section, we will discuss the dissociative adsorption of ethanol (and also acetaldehyde, since it is a major intermediate in the oxidation of ethanol) on Pt-based nanoparticle catalysts, and the identification of the resulting adsorbates/intermedi-ates on the basis of DBMS results. 

After reviewing ethanol and acetaldehyde dissociation on Pt-based nanoparticle catalysts, in this section we will discuss the effects of various factors, such as ethanol concentration, potential and catalyst composition on the current efficiencies, and product yields of the bulk electrooxidation of ethanol. 

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