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In China, they learned how to extract hydrogen from sea water without desalination plants and pumps - it can't be cheaper.
Sea water is an endless source of metals, minerals, drinking water, oxygen and hydrogen. For decades, scientists of all countries have been looking for an opportunity to extract these riches from the sea and ocean depths. The main task is to make the work cost-effective, but it is with this that all the barriers in the way of developers are connected. In China, they solved one of these problems - they learned how to easily produce hydrogen at no extra cost.
Hydrogen is extracted from water through the process of electrolysis. This is a simple and understandable operation, but only if this gas is extracted from clean water. Extracting hydrogen directly from sea water requires pre-desalination or very complex plants. Salts (ions) of metals and minerals dissolved in sea water destroy the catalysts of electrolyzers and other components of devices, as well as the operation of pumps for pumping sea water.
Scientists from the Nanjing Technical University in China in the journal Nature talked about a unique installation that is devoid of all the above disadvantages. Without pumps and rapid wear of catalysts, it is capable of extracting hydrogen and oxygen directly from sea water for a long time.
“Our strategy implements efficient, scalable, and scalable direct seawater electrolysis similar to freshwater splitting without a noticeable increase in operating costs,” said Zongping Shao, professor of chemical engineering at Nanjing Technical University in China.
An interesting solution has been proposed to protect catalysts from the effects of sea water—salts and ions. The catalyst-coated electrodes that produce hydrogen and oxygen (one at the cathode and the other at the anode) never come into contact with sea water. From this they are protected by a saturated electrolyte in the form of potassium hydroxide, in which these electrodes are immersed. How does water get there?
The electrolyte is protected by a membrane on both sides of the electrodes. The fluorine-rich membrane allows water vapor to pass through, but not liquid. Only water vapor enters the electrolyte through the membrane, leaving salts in the sea water. In the electrolyte, the steam turns back into water and splits into hydrogen and oxygen as desalinated water without negative consequences for the catalysts. Steam is pumped into the electrolyte due to external overpressure and does not require pumps.
Pumps are needed only for pumping sea water, but in the case of electrolysis with fresh water, they will also be needed, so this does not increase overhead. Moreover, it is convenient and profitable to extract minerals and metals from water with a high salt concentration, for example, the same lithium or uranium.
Researchers have proven the operation of the innovative installation in practice. A demonstrator of 11 electrolysis cells was lowered into the waters of Shenzhen Bay, where it worked non-stop for 130 days. Every hour the plant produced 386 liters of hydrogen. Electricity was spent only on pumping fresh sea water and on the electrolysis process itself. The system performed well in tests, although it is too early to talk about commercial implementation. Scientists plan to significantly improve its efficiency, which requires experiments with different compositions of the electrolyte and catalysts.