Researchers have synthesized hydrogen from seawater

Researchers at Pennsylvania State University have succeeded in producing dihydrogen from seawater.

The hydrogen industry, considered by some to be a serious alternative to fossil fuels, still needs to explore new ways of production to be virtuous. If this new technique does not solve the problem of the production of electricity necessary for electrolysis, it has at least the merit of exploiting a very abundant source of water.

The main defect of seawater: its salt!

Totally clean when it burns, hydrogen (called dihydrogen in its gaseous form) could become a major source of energy in the coming decades; however, the way to produce it is today the main obstacle to its expansion. Indeed, this molecule is very little present in the gaseous state in our atmosphere; it must therefore be extracted from other molecules. For this, several methods are used. Currently, almost all of the hydrogen produced (approximately 90%) comes from fossil fuels; not very green! But other alternatives exist, in particular the electrolysis of water.

This process involves passing an electric current through the water molecules, which separates hydrogen and oxygen. In itself, this technique is not polluting and does not emit CO₂. Only, it requires a lot of electricity, the latter not always coming from clean energies, far from it.

Its other flaw directly concerns water resources. Since fresh water is increasingly precious, diverting it to produce hydrogen is not ideal. On the other hand, using very abundant salt water could be a good alternative. For now, this process is only rarely used. And for good reason: the salt must imperatively be removed from the water before electrolysis, otherwise the chloride ions would be transformed into toxic chlorine gas, harmful to both the equipment and the environment. Furthermore, desalination is an expensive process. As a result, seawater has so far not attracted much interest in hydrogen production.

But researchers at Pennsylvania State University still want to explore this avenue: they have succeeded in producing hydrogen from seawater.

A promising process but still highly dependent on electricity production

Bruce Logan, professor of environmental engineering and professor at the University of Pennsylvania, summarizes: Hydrogen is a great fuel, but you have to make it. The only sustainable way to do this is to use renewable energy and produce it from water. You also have to use water that people don’t want to use for other things, and that would be seawater. So the holy grail of hydrogen production would be to combine seawater and hydrogen. ‘wind and solar power found in coastal and offshore environments’.

In order to get rid of the salt, the team replaced the ion exchange membranes typical of electrolysers with very fine semi-permeable membranes inherited from the reverse osmosis system. These membranes are inserted between the two immersed electrodes; near the anode, the water molecules split and release hydrogen ions (protons); then the latter move towards the cathode by crossing the membrane and combine with the electrons to form dihydrogen.

Bruce Logan explains: The idea is to exert very high pressure on the water and to push it through the membrane while keeping the chloride ions behind”.

But, as Bruce Logan reports above, this seawater-based electrolysis will only really be relevant when combined with electricity “ green “.

Source : HydrogenFuelNews