text: vulcan XC-72 is a type of "carbon black" which is essentially a name for any type of fine carbon powders; these powders are used for any number of industrial things, from pigments for ink to coatings and so on.\n\nin the case of fuel cells, it is a clumpy, aggregated carbon material on which the platinum is coated.  essentially it acts as a conductive support structure or substrate. according to the paper below, it is made of amorphous carbon nanoparticles that are 30nm - 60nm in size.  \n\nbecause this is a nanostructured material, the surface area (or "porosity") is very high, which is generally a good thin in electrochemical reactions, which take place at a solid-liquid interface.  more interface means faster reaction rate.\n\nit is made by cabot corporation: http://www.cabot-corp.com/cws/product.nsf/PDSDOCKEY/~~~VXC72?OpenDocument\nwhich sells it as an additive to insulators to increase the conductivity in power cables (i don't really understand why, but you can read about it:  http://w1.cabot-corp.com/controller.jsp?entry=market&N=23+4294966963+1000+4294967220 )