Hydrogen fuel cells generate electricity directly from hydrogen and generate zero carbon dioxide emissions, unlike conventional methods of electricity generation.
In order to accomplish this feat, a catalyst in the hydrogen fuel cell starts and maintains the reaction. Hydrogen in the fuel, typically pure hydrogen gas, is combined chemically with oxygen from the atmosphere, generating electricity and water vapor. The catalyst needs to be resilient to corrosion, which would quickly corrode and render useless most catalyst metals.
Noble metals, like platinum and gold, are immune to oxidation, but are also expensive. Currently, platinum and gold, the typical metals of choice for a hydrogen fuel cell catalyst, go for around $1,400/oz, or $44.8 million per ton. The reason I mention per ton is because iron goes for about $130 per ton or 0.4¢/oz. Platinum or gold based hydrogen fuel cell catalysts are very expensive.
As unlike as gold and rust are, they they work well together as a hydrogen fuel cell catalyst. Researchers at Duke University have devised a method to combine the noble properties of gold and near worthless iron oxide, otherwise known as rust, into a hydrogen fuel cell catalyst. The new catalyst is cheaper, which would reduce the cost of the fuel cell, but is also more efficient, eliminating the production of the poisonous gas carbon monoxide, a byproduct of inefficient hydrogen-to-water reaction.