Electrocatalysts high electrical conductivity

Silver films and Ag-CaO-SragOg cermets were chosen as the anodic electrocatalysts because of their high electrical conductivity, which is necessary for electrocatalytic operation, and also because of their high (>95%) selectivity to Cg hydrocarbons at very low (<2%) CH conversions [9]. 

Of practical importance is the contribution that is made by carbonaceous materials as an additive to enhance the electronic conductivity of the positive and negative electrodes. In other electrode applications, carbon serves as the electrocatalyst for electrochemical reactions and/or the substrate on which an electrocatalyst is located. In addition, carbonaceous materials are fabricated into solid structures which serve as the bipolar separator or current collector. Clearly, carbon is an important material for aqueous-electrolyte batteries. It would be very difficult to identify a practical alternative to carbon-based materials in many of their battery applications. The attractive features of carbon in electrochemical applications are its high electrical conductivity, acceptable chemical stability, and low cost. These characteristics are important for the widespread acceptance of carbon in aqueous electrolyte batteries. 

Carbon-supported platinum (Pt) and platinum-rathenium (Pt-Ru) alloy are one of the most popular electrocatalysts in polymer electrolyte fuel cells (PEFC). Pt supported on electrically conducting carbons, preferably carbon black, is being increasingly used as an electrocatalyst in fuel cell applications (Parker et al., 2004). Carbon-supported Pt could be prepared at loadings as high as 70 wt.% without a noticeable increase of particle size. Unsupported and carbon-supported nanoparticle Pt-Ru, ,t m catalysts prepared using the surface reductive deposition... 

Electrodeposition. In this process, a conductive substrate is placed in an electrolyte solution (typically aqueous) that contains a salt of the material of interest. When an electrical potential is apphed between the substrate and a counter electrode, redox chemistry takes place at the surface of the substrate which deposits material. Complex pulse trains and/or high-pulse frequencies are sometimes used to direct current flow and favor desired reactions. A postsynthesis calcination is often performed to reach a desired material phase. Electrodeposition is restricted to deposition of electrically conductive materials and produces polycrystaUine and amorphous films. This process is also appropriate for thin film surface treatment of PEC electrodes, such as electrocatalyst deposition. 

In recent decades, various electrode materials have been investigated to improve the performance of fuel cells [299]. A conventional low-temperature fuel cell electrode is composed of polytetrafluoroethylene, a high-surface-area carbon black loaded with a precious metal catalyst, and a current collector, as well as other minor components. The most challenging issue for electrode performance is the electrocatalyst [327]. Carbon has been established as the best catalyst support because of its good electrical conductivity, high surface area, surface hydro-phobicity, and stability [328-331]. In the past few years, template-synthesized carbons with various structures have been tried as components of fuel cells. 

It is essential to minimize any voltage loss in fuel cells and water electrolysis for energy conversion. As a result, highly sophisticated membrane electrode assemblies (MEA) have been developed to optimize contact between the membrane and the electrocatalyst in the electrodes. Similarly, for the first organic SPE electrosyntheses [2], electrically conductive porous platinum or gold layers inside of the surfaces of Nation membranes were used, prepared by a chemical method similar to [7]. 

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