New Process Makes Hydrogen from Water

A research team at the University of Tokyo has developed a way to use visible light to dissociate water and make hydrogen gas, which can be used as a renewable energy source.

Water photolysis to yield hydrogen and oxygen is not new, but conventional systems exclusively use short-wavelength ultraviolet light, which only accounts for around 5% of the total light energy from the sun. Since visible light makes up roughly 50% of the wavelengths of sun rays, tapping into this part of the spectrum makes the photolysis process far more efficient.

The setup developed by Professor Kazunari Domen’s research team consists of a large sealed glass water tank with a propeller screw for mixing. The photolysis reaction is sparked by gallium nitride and zinc oxide powders instead of the titanium oxide normally used as the catalyst for water photolysis. These compounds can glean the energy from wavelengths of 400-500nm in the visible part of the spectrum. The researchers will work to add more catalytic compounds in order to tap wavelengths as long as 600nm, effectively using half of the visible light spectrum.

The goal is to have a practical machine ready in five years that can produce hydrogen as fuel for cars. The idea is to attach the glass water tank to a device that selectively removes hydrogen gas from the reaction so it can be stored and supplied as a fuel.