Silicon passes a test in water-splitting

The use of solar energy to split water into hydrogen and oxygen is an appealing idea, given that sunlight is abundant in many parts of the world, but one of the challenges to its development is to find a suitable electrode material. Silicon, the popular photovoltaic material, seems like a logical choice, but when it is exposed to O2 it is rapidly oxidized and fails. Researchers at Stanford University (Stanford, Calif.; www.stanford.edu) may have a solution. Using atomic layer deposition, a common process in semiconductor manufacturing, they have deposited a 2-nm protective coating of titanium dioxide on silicon electrodes, followed by a similar, evaporated layer of iridium. TiO2 is transparent to sunlight and the iridium boosts the rate of the splitting reaction, says Paul McIntyre, of Stanford’s Materials Science and Engineering Dept. In laboratory tests the coated electrodes have shown stable operation for more than 24 h, without apparent corrosion or loss of efficiency, he says, while uncoated electrodes corroded and failed in less than 30 min. Next, the researchers plan to scale up the process and test other semiconductor materials. The ultimate goal, says McIntyre, is the development of a commercial process in which H2 and…