Will Water Become the Ultimate Mobile Fuel? (February 21, 2013)

As reported in this week's Nature: Silicon reacts extremely slowly with water to produce hydrogen gas, but 10-nanometre-wide silicon particles react 1,000 times faster.

Mark Swihart, Paras Prasad and their colleagues at the State University of New York at Buffalo report that 1 gram of powdered silicon can generate about 2 litres of hydrogen in about 45 seconds — a rate that is sufficient for systems to produce hydrogen fuel on demand from water.

The authors say that the process they used to generate the silicon powders — breaking up silane gas with lasers — can produce kilograms of powder in an hour, which may mean that the process has the potential to move beyond niche applications.

The abstract of the paper in Nano Letters (Nano Lett., 2013, 13 (2), pp 451–456; DOI: 10.1021/nl304680w) reads:

We demonstrate that nanosize silicon (10 nm diameter) reacts with water to generate hydrogen 1000 times faster than bulk silicon, 100 times faster than previously reported Si structures, and 6 times faster than competing metal formulations. The H₂ production rate using 10 nm Si is 150 times that obtained using 100 nm particles, dramatically exceeding the expected effect of increased surface to volume ratio. We attribute this to a change in the etching dynamics at the nanoscale from anisotropic etching of larger silicon to effectively isotropic etching of 10 nm silicon. These results imply that nanosilicon could provide a practical approach for on-demand hydrogen production without addition of heat, light, or electrical energy.