Hydrogen fuel cells promise clean cars that emit only water. Several major car manufacturers have recently announced investments to increase the availability of fueling stations, while others are rolling out new models and prototypes. However, challenges remain, including the chemistry to produce and use hydrogen and oxygen gas efficiently.

Hydrogen (H2) fuel cells combine H2 and oxygen (O2) gases to produce energy. For that to happen, several related chemical reactions are needed, two of which require catalysts.

The first step is to produce the two gases separately. The most common way to do that is to break down, or “split,” water with an electric current in a process called electrolysis. Next, the fuel cell must promote the oxidation of H2. That requires reduction of O2, which yields water.

Yi Cui, an associate professor of materials science and engineering at Stanford and of photon science at SLAC National Accelerator Laboratory, worked on the first reaction, developing a new cadre of porous materials for water splitting. Cui’s team used Earth-abundant cobalt-nickel-iron oxides, splitting water continuously for more than 100 hours, significantly better than what researchers have reported for most other non–precious metal materials.