Saturday, April 28, 2012


Two teams of researchers in the US have taken important steps towards the creation of commercially viable"artificial leaf"– a hypothetical device that can turn sunlight into electrical energy or fuel by mimicking some aspects of photosynthesis.

Earlier this year, the chemist Daniel Nocera at the Massachusetts Institute of Technology (MIT) announced artificial-leaf prototypes.

Now, working with two different teams of researchers, he has published two papers on different devices that represent progress towards effective and commercially viable versions of the artificial leaf.

Both teams made their devices from silicon wafers that are coated with catalytic metals and protective layers.

The prototype solar cells are about the size of a credit card and can capture
sunlight and then use the energy to split water into its constituent oxygen and hydrogen.

This is different to conventional photovoltaic cells, which convert light directly into electricity.

With these new devices, the ultimate plan is to recombine the two gases in an integrated fuel cell, thus converting the chemical energy to electrical energy.

Producing fuel rather than electricity has the advantage that the fuel can be easily stored until it is needed.

Both artificial leaves use a silicon n–p junction: a bilayer of n-type and p- type silicon. An incident photon is absorbed to create an electron–hole pair in the semiconductor. The electrons migrate to the n-side and the holes to the p-side.

The holes then drive the splitting of water in a process mediated by the outermost layer of the cell, which is a photocatalyst.