Water-splitting device solves puzzle of producing hydrogen direct from seawater

A combined desalination–electrolysis system that can produce green hydrogen directly from seawater has been developed by a team in China. This integrated process uses a low energy method to purify seawater, making it the first viable approach to use salt water as a source of hydrogen. The purification step uses phase transitions to remove impurities and could have additional applications in wastewater treatment and resource recovery.

Splitting water with electricity has been experimented with for over 200 years and the reactions involved are well-understood: at the cathode, H+ ions gain electrons to form hydrogen gas whilst OH- loses electrons at the anode to form oxygen. But despite the simplicity of the underlying chemistry, effective electrolysis is a particularly complicated process. Water splitting is thermodynamically unfavourable and requires both specifically designed catalytic electrodes and a significant input of energy to drive the reaction. Even trace impurities can damage the delicate structure of the cell, leading to membrane pores becoming blocked, expensive electrodes corroded and unwanted byproducts formed.