'Artificial Leaf'-A New Energy Source

Researchers from Massachusetts Institute of Technology have invented the world's first artificial leaf that can turn water into hydrogen and oxygen with the help of sunlight without needing any external connections, is seen with some real leaves, which also convert the energy of sunlight directly into storable chemical form.

Researchers led by MIT professor Daniel Nocera have produced something they’re calling an “artificial leaf”: Like living leaves, the device can turn the energy of sunlight directly into a chemical fuel that can be stored and used later as an energy source.

In this a silicon solar cell with different catalytic materials bonded onto its two sides which needs no external wires or control circuits to operate. Bound onto the silicon is a layer of a cobalt-based catalyst, which releases oxygen, a material whose potential for generating fuel from sunlight was discovered by Nocera and his co-authors in 2008. The other side of the silicon sheet is coated with a layer of a nickel-molybdenum-zinc alloy, which releases hydrogen from the water molecules.
When Simply placed in a container of water and exposed to sunlight, it quickly begins to generate streams of bubbles: oxygen bubbles from one side and hydrogen bubbles from the other. If placed in a container that has a barrier to separate the two sides, the two streams of bubbles can be collected and stored, and used later to deliver power: for example, by feeding them into a fuel cell that combines them once again into water while delivering an electric current.

An "artificial leaf" made by Daniel Nocera and his team, using a silicon solar cell with 
novel catalyst materials bonded to its two sides, is shown in a container of water with   
light (simulating sunlight) shining on it. The light generates a flow of electricity that 
causes the water molecules, with the help of the catalysts, to split into oxygen and 
hydrogen, which bubble up from the two surfaces.

The device, Nocera explains, is made entirely of earth-abundant, inexpensive materials — mostly silicon, cobalt and nickel — and works in ordinary water. Other attempts to produce devices that could use sunlight to split water have relied on corrosive solutions or on relatively rare and expensive materials such as platinum.