Hydrogen as an energy source could become an essential cornerstone of a new, CO 2 -neutral energy supply.
Ideally, the necessary electrolysis of water is driven by renewable energy sources such as sun, water, geothermal energy, or wind. However, the current state of the art requires water of drinking water quality for this type of electrolysis – an increasingly expensive commodity worldwide. Together with international colleagues, Prof. Dr. Peter Strasser, head of the technical chemistry department at the TU Berlin, has now published a study on the possibilities and technical challenges of electrolysis of saltwater in the journal Nature Energy.
Hydrogen, obtained from the solar-powered electrolysis of water, offers itself as a CO 2 -neutral and storable and transportable energy source, especially for arid, arid regions of the world. However, the water of drinking water quality required for electrolysis is a valuable resource worldwide. Arid areas in particular, which potentially have sufficient solar energy, are often close to the oceans, but usually suffer from a blatant lack of freshwater. In turn, the purification of saltwater is a costly and CO 2 intensive process, which makes the process uneconomical and, above all, no longer climate neutral.
“To enable the use of solar and hydrogen technology in these regions in particular, researchers worldwide are trying to develop an electrolysis technology that is able to split saltwater directly into hydrogen and oxygen without a prior desalination step,” says Weiß Peter Strasser, whose own research team at the TU Berlin deals intensively with different processes and catalysts for hydrogen electrolysis. “The hydrogen obtained in this way could then be transported directly in the form of liquid hydrogen, but also after further local conversion into synthetic liquid methane or synthetic gasoline on ships or in pipelines, and thus facilitate the switch to hydrogen-based energy infrastructure,” said the scientist.
Peter Strasser and his colleagues from the National University of Ireland Galway and the University of Liverpool analyzed all international publications that report successful electrolysis of saltwater. This enabled them to uncover the main challenges that need to be overcome in order to make this future form of electrolysis competitive. “According to our analysis, future research should focus on the use of new types of catalyst materials as well as suitable membranes. The membranes commonly used in electrolysis are often unable to block the salt impurities in the water, ”says the chemist. A potentially interesting approach is the use of membranes, which are modeled on the membranes in certain plants such as mangrove roots. These plant membranes can filter seawater. If similar membranes were used in technical electrolysis, the salt concentration on the surface of the catalytic electrodes could be reduced and membrane contamination could be reduced.
“As part of our study, we showed that the development of new selective catalysts and special membrane technology are important steps towards high-performance saltwater electrolysis and should be researched more intensively in the future,” said Peter Strasser. “In our opinion, the use of freshwater to produce hydrogen in large quantities will not remain a viable option in the long term, especially not in the arid regions where most of the cheap solar power is generated,” the scientist added.