Why use an alloy catalyst?
For pure hydrogen, platinum is an excellent catalyst, but many fuel cells today use reformate (reformed hydrocarbons) or methanol as fuel. Ideally, reformate is a blend of hydrogen and carbon dioxide, possibly containing water vapor. Realistically, reformate is rarely this pure. Most reformate contains traces of carbon monoxide (CO). Even at low levels, CO quickly poisons pure platinum catalysts. Some platinum alloys, such as Pt-Ru, have substantially greater resistance to poisoning by CO. Methanol, the fuel used in direct methanol fuel cells (DMFC), has a similar effect on platinum. In this case as well, alloy catalysts frequently have better resistance to poisoning than pure platinum.
