Hydrogen is considered the hope of the energy transition - it should be used as a fuel for aircraft, ships and trucks, as a raw material for industry or as a fuel for heating. If it is generated from water with renewable energy, the production is even almost climate -neutral. However, there are often not enough water for electrolysis in particularly sun or windy regions. A research group around the chemical engineer Gang Kevin Li from the University of Melbourne has therefore developed a prototype that absorb moist air, withdraw the water and split it directly into the two gases oxygen and hydrogen. The principle presents them in "Nature Communications".
In order to reduce carbon dioxide emissions in industry, hydrogen (H2) is extremely important. If it is burned, only water is produced. In the case of particularly energy-intensive steel production, hydrogen should one day replace coal. Certain processes in the chemical industry can only be made climate-friendly with green hydrogen. And gas-fired power plants will also be operated with H2 in the future. True, hydrogen is the most common chemical element in the universe. On earth, however, it occurs almost exclusively bound in the form of water.
Existing large -scale systems for electrolysis often require complex material components, rare metals and access to pure fresh water. This can lead to a competition for the already limited drinking water supplies in some parts of the earth. These factors have so far driven the cost of hydrogen production and have a wide range of use.
Gang Kevin Li and his colleagues want to get around this problem and access water supplies that can be found even in the driest areas of the world, such as in the Sahara desert or in the Australian outback. "There are 12.9 trillion tons of water in the air at any one time," the scientists write, "universally available and inexhaustible." All it takes is efficient systems to be able to access it. You have now shown that this is possible. Up to a minimum relative humidity of four percent, hydrogen can still be generated with this so-called "direct air electrolysis" (DAE).
The core of your electrolysis cell is a porous substance soaked with sulfuric acid, which on the one hand serves as an electrolyte and, on the other hand, removes the moisture. The researchers used platinum as electrode material. They operated their module with solar energy and tested it for eight hours each twelve days at a time. They caught the hydrogen, they let the oxygen escape. So they came to an average of 93 liters of pure hydrogen per hour and square meters of the cathode material.
Although the authors write that their electrolysers are scalable, they do not comment on the costs or the possible environmental impact of their technology.
