Wouldn't it be nice to have a machine that could cheaply manufacture a gallon of gas per hour for your automobile? Envisioning the day when we may all have fuel cell cars, General Electric researchers have built a prototype that makes the equivalent quantity of hydrogen: plug it in, and it splits water molecules to generate one kilogram per hour of hydrogen.

The basic technology, called an electrolyzer, is nothing new: water is mixed with an electrolyte and made to flow past a stack of electrodes. Electricity causes the water molecules to split into hydrogen and oxygen gases. What GE has achieved is a potentially inexpensive, mass-manufacturable version of the technology.