Chemists develop corrosion-free method to extract hydrogen from seawater
Scientists from the American Stanford University have developed a method for extracting hydrogen gas from seawater via electrolysis, whereby no or very limited corrosion occurs at the anode to be used.
Hongjie Dai, professor of chemical sciences, explains that most existing water splitting methods are based on highly purified water. However, its availability is a problem. Seawater is available in almost infinite quantities, but its salt quickly leads to corrosion at the anode, limiting the life of an electrolysis system with electrodes placed in the water. Dai and his fellow scientists have used a different material for the anode in their electrolysis process to counteract this negative corrosion effect.
The researchers found that if they coated the positive anode with metal layers rich in negatively charged ions, the corrosive chlorine ions are repelled or kept away from the anode. This slows the degradation of the underlying metal of the anode. According to the scientists, a regular anode in seawater only works for 12 hours before it breaks down due to rust. However, with the negatively charged coating, the anode can ‘last more than a thousand hours’. The researchers also managed to maintain the electric current well, so that hydrogen production did not significantly decrease.
The production of hydrogen by splitting seawater has been done before in previous studies, but according to the Stanford researchers, a lower voltage was often used. After all, corrosion only occurs at a higher voltage. Dai and the other researchers eventually managed to feed up to ten times as much electricity through their system, which also produced the hydrogen at a faster rate. According to Dai, this is likely to set a record for the amount of electricity used to split seawater.
A proof-of-concept was shown in the lab, but the researchers leave it up to manufacturers to scale up the design and actually use it in mass production. The voltage could be regulated in the laboratory, but the researchers have also designed a system based on solar energy that produces hydrogen and oxygen from seawater. According to the scientists, what is impressive about their study is that they managed to operate their system at a voltage comparable to that of current industrial technology for extracting hydrogen from purified water.
The scientists state that their invention for seawater electrolysis could lead to a greater availability of hydrogen as a fuel, which is generated by solar or wind energy. The researchers are also looking beyond generating hydrogen as an energy source. The process also produces oxygen gas, which is breathable. That means divers or submarines can be equipped with the system to generate oxygen underwater without having to come to the surface.
The research is published in the scientific journal PNAS under the title Solar-driven, highly sustained splitting of seawater into hydrogen and oxygen fuels.