Advanced Electrocatalyst Support Materials

Electrodes consisting of supported metal catalysts are used in electrosynthesis and electrochemical energy conversion devices (e.g., fuel cells). Nanometer-sized metal catalyst particles are typically impregnated into the porous structure of an sp -bonded carbon-support material. Typical carbon supports include chemically or physically activated carbon, carbon black, and graphitized carbons [186]. The primary role of the support is to provide a high surface area over which small metallic particles can be dispersed and stabilized. The porous support should also allow facile mass transport of reactants and products to and from the active sites [187]. Several properties of the support are critical porosity, pore size distribution, crush strength, surface chemistry, and microstructural and morphological stability [186]. 

A limitation of sp -bonded carbon supports is their susceptibility to corrosion and microstructural degradation during anodic polarization. One possible carbon electrochemical corrosion reaction is [188] 

Conductive sp -bonded diamond is being developed as an advanced catalyst support material. Boron-doped diamond thin-film electrodes possess excellent properties for this application, such as electrical conductivity, chemical inertness, extreme corrosion resistance, and dimensional stability. Compared with more commonly used sp -bonded carbon materials, diamond is highly resistant to electrochemical corrosion. For exam- 

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X. OPTICALLY TRANSPARENT ELECTRODES FOR SPECTROELECTROCHEMISTRY 239 XL ADVANCED ELECTROCATALYST SUPPORT MATERIALS 251... 

Part VI discusses novel advanced electrocatalytic materials, including polymer-embedded nanoparticle electrodes for PEM fuel cells and synthetic diamond-supported electrocatalyst nanoparticles for toxic organic compound treatment. 

Non-precious metal catalyst research covers a broad range of materials. The most promising catalysts investigated thus far are carbon-supported M-N /C materials (M = Co, Fe, Ni, Mn, etc.) formed by pyrolysis of a variety of metal, nitrogen, and carbon precursor materials [106]. Other non-precious metal electrocatalyst materials investigated include non-pyrolyzed transition metal macrocycles [107-122], coti-ductive polymer-based complexes (pyrolyzed and non-pyrolyzed) [123-140], transition metal chalcogenides [141-148], metal oxide/carbide/nitride materials [149-166], as well as carbon-based materials [167-179]. The advances of these types of materials can be found in Chaps. 7-10 and 12-15 of this book. 

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