But, now General Motors scientistis have found a cheaper material, perovskite, that works about as well, but is much cheaper.
[P]erovskite oxides made of cobalt or manganese combined with oxygen. By adding a bit of strontium and lanthanum into the mix, . . . manganese-based perovskite catalysts converted NO to NO2 about as well as platinum-based ones did. The cobalt-based perovskite catalyzed the reaction at rates significantly higher than platinum. . . . The new catalysts are not, however, entirely free of precious metals. The team had to add a bit of palladium – which goes for about one-quarter the cost of platinum – to eliminate some sulfur buildup.
The result may be a new generation of less expensive diesel vehicles. This is good news because diesel engines are more fuel efficient, are reliable because they have simpler designs (they don't need spark plugs), and are more easily adapted to biofuels. The process for making biodiesel is easier than the process for making biofuel substitutes for gasoline, such as ethanol.
Diesels have long been more popular in Europe than in the United States, because fuel is more expensive there making fuel efficiency more important. But, it is only a matter of time before the United States faces similar economic pressures.