Nanoparticles of silicon can be made to react instantly with water to produce hydrogen without application of any heat, light or electricity.

Hydrogen production

Traditional techniques to split water to produce hydrogen include electrolysis, thermolysis and photo catalysis.But bulk silicon abundantly available on earth can react slowly with water to produce hydrogen by releasing two moles of hydrogen gas per mole of silicon without releasing any carbon dioxide.

Nanosilicon

Silicon nanoparticles due to their high surface to volume ratio can generate hydrogen quickly than bulk silicon due to high reaction rate. Researchers at the University at Buffalo (SUNY) in New York have developed this technique.

For example nanoparticles 10 nm in size can produce hydrogen in under a minute which is1000 times faster at producing hydrogen than is bulk silicon and nanoparticles of 100 nm in diameter can produce at 45 minutes.

During the hydrogen production reaction, the 10 nm silicon particles reduce in size, but do not change shape, where as the 100 nm particles do not uniformly reduce in size, but form hollow shells or capsules with walls of a few monolayers of silicon which then slow down the water-silicon reaction due to the formation of an extra layer through which the reactants must diffuse.

Applications

According to the researchers this technology can be used for powering small portable devices and might even replace bulky gasoline or diesel generators in the future and a typical silicon generator could comprise a small hydrogen fuel cell and some plastic cartridges of silicon nanopowder, to which water would be added when needed, to produce energy.

The overall efficiency of hydrogen production could be quite competitive with primary batteries and other sources of portable power.

Nanoballoons

Also hollow nanoballoons can be produced by reaction of the larger silicon particles by mixing with other materials such as alkali hydrides to make anodes for lithium-ion batteries. Alkali metal hydrides react with water to release hydrogen and produce alkali metal hydroxides like sodium hydroxide needed to catalyse the silicon reaction with water by making them stable due to silicon nanoparticles coating.