The Massachusetts Institute of Technology unveiled a prototype solar-powered device the size of a playing card that can break water down into hydrogen and oxygen – valuable fuels for producing electricity via fuel cells. This new artificial leaf combines the solar cell and the electrolysis unit into one piece by chemically painting the catalyst onto a solar cell and immersing it in water.

The chemistry is complex but is similar from a systems engineering sense to the manner in which leaves generate energy from sunlight. In plants, the energy of incoming sunlight is first used to produce electrons and positive charges within the leaf. These are then used to split water into oxygen and hydrogen (the latter being trapped as carbohydrates, rather than released into the air). In his artificial leaf, a silicon chip, similar to those used in conventional solar cells, produces electrons and positively charged holes. Then catalysts on the chip use this low-voltage current to produce oxygen and hydrogen – one gas on each side of the chip.