Photoelectrochemical Cell

A photoelectrochemical cell is a device that uses light striking a semiconductor electrode immersed in an electrolyte to drive a chemical reaction directly, and in its water splitting form, sometimes called a photoelectrolytic cell, the process is described as a kind of artificial photosynthesis that stores solar energy as hydrogen fuel. Light excites electrons in the semiconductor electrode, which travel through an external circuit to a counter electrode where they combine to form hydrogen gas, while the holes left behind in the semiconductor oxidize water at its surface to release oxygen. French physicist Alexandre-Edmond Becquerel built the first photoelectrochemical cell, and the first photovoltaic device of any kind, in 1839 at the age of nineteen, but the modern field began in 1972 when Akira Fujishima and Kenichi Honda reported splitting water electrochemically at a titanium dioxide electrode under light, a discovery that launched decades of research into titanium dioxide based systems. Photoelectrolytic cells have since passed ten percent solar to hydrogen conversion efficiency, though corrosion of the semiconductor electrode remains a persistent problem; the United States Department of Energy has set a target service life of 10,000 hours, and recent silicon nickel electrode designs have reached 80 hours of stability while vapor fed systems have sustained 14 percent efficiency for more than 1,000 hours.