The traditional method of extracting hydrogen using electrolysis requires nine liters of fresh water to produce every kilogram of hydrogen. Taking into account the shortage of water resources, the course for hydrogen is doubtful. The use of untreated sea water could be a solution, but until recently there was no acceptable technology for the direct extraction of hydrogen from ocean waters.
The solution was found by scientists from Australia in collaboration with colleagues from Tianjin and Nankai Universities in China and the University of Kent in the USA. The researchers say they have developed a way to improve conventional commercial electrolyzers that can break down seawater with “nearly 100 percent efficiency” without any pre-treatment other than filtration.
Conventional metal catalysts based on platinum and other precious metals require long and complex preparation of sea water for hydrogen production. Scientists were able to adapt cheap cobalt oxide and chromium oxide catalysts for this, but pre-treated their surface with the so-called Lewis acid. Under normal conditions, chloride ions from sea water destroy such compounds, or the water clogs the catalysts with insoluble precipitates of magnesium and calcium compounds, which quickly reduces the working surface area. The addition of acid blocks all destructive chemical processes and allows inexpensive catalysts to last longer even in such an unprepared environment.
“We split ordinary sea water into oxygen and hydrogen with almost 100 percent efficiency to produce environmentally friendly hydrogen by electrolysis using a non-precious and cheap catalyst in a commercial electrolyzer,” said Professor Shizhan Qiao.
“The performance of a commercial electrolytic cell with our catalysts operating in sea water is close to the performance of platinum/iridium catalysts operating on a feedstock of highly purified deionized water,” added another author of the work.
The proposed method was tested in laboratory conditions on a small installation. At the next stage, scientists will try to scale the solution to approach the stage of commercial implementation. The most important thing in the development is the possibility of a simple refinement of existing electrolyzers, but there are other equally interesting technologies for extracting hydrogen from untreated sea water. Sooner or later, some of this will have to be adopted.
A nice bonus to the extraction of hydrogen from sea water is the production of fresh water and useful resources. All this is regarded as an opportunity to develop factories for the extraction of valuable resources on the coasts of the seas and oceans.
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