Researchers discover way to generate hydrogen fuel from sea waterOctober 2, 2020
The Penn State team use membranes to extract the salt from the water to help split the molecule.
A team of Penn State researchers have found a way to produce hydrogen fuel from sea water using purification technology integrated into a new proof-of-concept electrolyzer design.
This method uses electric current to split the water molecules into the fuel and oxygen.
The idea behind being able to make hydrogen fuel from sea water is to make it easier to power green fuel generation through wind and solar energy. In this way, these renewable sources of electricity can be converted into fuel that can be stored and transported, said Bruce Logan, professor of environmental engineering and Evan Pugh University professor.
“Hydrogen is a great fuel, but you have to make it,” said Logan. “The only sustainable way to do that is to use renewable energy and produce it from water. You also need to use water that people do not want to use for other things, and that would be sea water. So, the holy grail of producing hydrogen would be to combine the sea water and the wind and solar energy found in coastal and offshore environments.”
Hydrogen fuel from sea water is not a common process, despite the abundance of the source.
The issue is that the salt in ocean water must be removed before it can enter the electrolyzer. Desalinating is an expensive process, which has meant that this source of water has not had much appeal for traditional H2 production. If the salt were to be left in place during electrolysis, the chloride ions convert into toxic chlorine gas, which damages both the equipment and the environment.
In order to prevent such damage, the research team used a thin, semipermeable membrane. The membrane was originally developed for reverse osmosis (RO) water purification treatment. That membrane replaced the ion-exchange membrane that is a typical component in electrolyzers.
“The idea behind RO is that you put a really high pressure on the water and push it through the membrane and keep the chloride ions behind,” explained Logan.
During this process of producing hydrogen fuel from sea water, the water would not be forced through the RO membrane. Instead, the membrane would contain it. The membrane is employed for separating reactions taking place near two submerged electrodes – a negatively charged cathode and a positively charged anode – which are connected by way of an external source of electricity. Once the electricity is turned on, the water splits near the anode, releasing protons (hydrogen ions) and producing oxygen gas. From there, the protons pass through the membrane to the cathode where they combine with electrons and form H2.