Carbon corrosion surface porosity

The instantaneous MEA materials structural evolutions (e.g. ECSA, carbon surface area, PEM porosity) in the simulated PEMFC operation, induced by catalyst dissolution and ripening, carbon corrosion and PEM chemical degradation, are determined at each simulation time-step as functions of the elementary degradation chemistry kinetic equations as described. ... 

The corrosion product is predominantly carbon dioxide, but considerable amounts of free oxygen are produced at the anode surface, particularly in fresh-water applications, and can attack both the carbon and any organic binders used to reduce its porosity. For this reason carbon anodes for underground service are used in conjunction with a carbonaceous backfill. 

Button cells consist of cathode and anode cans (used as the terminals), powdered zinc anode, containing gelled electrolyte and the corrosion inhibitor, separator with electrolyte, thin (0.5 mm) carbon cathode with catalyst and PTFE, waterproof gas-permeable (teflon) layer and air distribution layer for the even air assess over the cathode surface. Parameters of battery depend on the air transfer rate, which is determined by quantity and diameters of air access holes or porosity of the gas-diffusion membrane. Air-zinc batteries at low rate (J=0,002-0,01C at the idle drain and J= 0,02-0,04C at the peak continuous current) have flat discharge curves (typical curve is shown by Figure 1). 

A very detailed fuel cell-related TEM study of CB and CB corrosion can be found in Eiu et al. [15]. Gas adsorption, Hg intrusion porosimetry, and small-angle X-ray scattering (SAXS) provide information on porosity and pore size distribution, each of them having its own advantages and limitations. Methods that can be used to probe the functional groups at the carbon surface are X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption spectroscopy (NEXAES). Table 7.1 gives an overview of characterization techniques applied... 

The uniformity of phosphate films is influenced by the surface condition of the base metal and the nucleation of phosphates. Carbonaceous residues on steel surfaces resulting from rolling lubricants during the annealing of steels have an effect on the corrosion performance of paint-phosphate-coated steels. The porosity of a phosphate film is increased as a result of carbon contamination on the steel surface, which promotes the formation of defects in the film. 

The support for the metal nano-particles turns out to be as important as the nano-particles for providing their dispersion and stability. Studies on electron transfer are particularly important for carbon-based materials because those materials, such as glassy carbon, graphite, fullerene, and diamond with different electronic and structural properties, have been proved to possess distinctly different electrochemical properties from each other (Ramesh and Sampath, 2003). Carbon supports provide high electronic conductivity, uniform catalyst dispersion, corrosion resistance, and sufficient access of gas reactants to the catalyst (Ismagilov et al, 2005). In addition to electrical conductivity and surface area, hydrophobicity, morphology, porosity, and... 

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