Green hydrogen is considered a key element in the energy transition: Produced with solar or wind power, it can be processed into carbon dioxide-neutral fuels, for example, or used in industry, such as in steel production. In addition to clean energy, water is needed as a starting material. This is available on Earth primarily in the oceans.
Of course, salt water can also be split by electrolysis. But because of the high salt content, this is not very effective: chloride ions migrate to the positively charged electrode, which can prevent the water's hydroxyl groups from attaching.
To counteract this, potassium hydroxide could be added to the water in large quantities. However, this would increase the effort and thus the cost.
Seawater does not need to be pretreated
A team from Australia, China and the USA is pursuing a different approach: It has developed an electrolyzer that generates hydrogen from seawater without the need for pretreatment. To this end, the team led by Tao Ling constructed an electrode made of nanostructured cobalt oxide. A thin Lewis acid layer is applied to it. In the specific case, this is chromium oxide. Electron pairs in particular attach themselves to this Lewis acid. As a result, hydroxyl groups reach the electrode more easily and more frequently than chloride ions.
The advantage of this solution, which additionally helps to make progress with the Sustainable Development Goals, is that no fresh water is needed for electrolysis. In the future, such plants will probably be built in regions where the yield of solar energy is particularly high. However, fresh water is often in short supply there. Salt water, on the other hand, is available in large quantities. Accordingly, other research groups are also looking into the electrolysis of seawater. At the end of last year, a team from Shenzhen University in southeastern China presented such a system. Ling's team writes in the journal „Nature Energy“ that the system has proven remarkably efficient in laboratory tests. The next step is to make the system more stable as well as to scale it up.
Ultimately, how much money automakers, fuel station builders, energy corporations, and governments are ready to invest in green hydrogen over the coming years will determine whether or not it lives up to its potential and promises.
Green hydrogen has a lot of sustainable potential. It can be applied to every industry. Because it addresses the most challenging aspects of the issue—industry and heavy transportation. Additionally, there are several green and blue ways to produce hydrogen with no carbon. With biohydrogen, the global society even produce hydrogen with negative carbon. The options are versatile. It just needs a strong network of a global society that is willing to take action.