Scientists at the University of California, Santa Cruz (UCSC) have developed a new method to efficiently generate hydrogen from water at ambient temperatures using aluminum and gallium.
The research was published in the journal Applied Nano Materials in February and has a US patent application.
Aluminum is an excellent candidate material for this purpose because the highly reactive metal readily reacts with oxygen molecules in water to release hydrogen gas. But the pure form of the metal is so reactive that it immediately reacts with air to create a layer of aluminum oxide on its surface, meaning it cannot react with water.
This is where gallium comes in. Gallium is liquid at slightly above room temperature and removes the aluminum oxide coating that forms on the bare metal, allowing it to come into direct contact with and react with water. The reaction of aluminum and gallium with water to produce hydrogen gas is already common scientific knowledge, but the new technology contains innovations that bring it closer to practical applications.
According to the researchers, previous such studies focused mainly on the use of aluminum-rich compounds. But they found that using a gallium-rich mixture led to an unexpectedly high rate of hydrogen production.
“After the process, we can easily recover 95 percent of the gallium used, without optimization. The only other product that was formed was Alumina [Aluminium Oxide]which can be used for many other applications,” Scott Oliver, corresponding author of the research paper, told indianexpress.com via email.
This is important because gallium is an expensive and rare mineral. Alumina has many applications including spark plugs, wear resistant plates and cutting tools.
Because of the new compound ratio, not only was the gallium removing the aluminum oxide coating, it was also breaking down the aluminum into nanoparticles, which helped speed up the reaction. The researchers found that a 3:1 ratio of gallium to aluminum in the composite was the optimal ratio for the highest hydrogen production. Moreover, the composite is very easy to form. The researchers created it by manually mixing small amounts of aluminum into gallium.
While it remains to be seen whether this technology can be scaled up to produce hydrogen in commercial quantities, researchers are optimistic. “It should be possible to scale up the technology to industrial production levels. We were limited only by our apparatus to measure the volume of hydrogen and the limits of the campus in hydrogen. Scaling up will require control of the alloy mix, but the reaction is spontaneous once water is added,” Oliver added.
The worldwide push for electric vehicles has focused primarily on battery electric vehicles (BEVs), which typically use lithium-ion batteries to store electricity that can be used to propel the vehicle using electric motors. An alternative technology involves using “hydrogen fuel cells” to generate electricity from hydrogen and use it to power the vehicle.
Hydrogen fuel cell vehicles offer several advantages over BEVs—they can be refueled with hydrogen as quickly as a conventional vehicle can be refueled with fossil fuels. They also reduce dependence on minerals such as lithium and cobalt, which are used to make lithium-ion batteries.
But using hydrogen comes with a major disadvantage. According to the US Department of Energy, most of the world’s hydrogen gas production comes from reforming fossil fuels such as natural gas. And producing hydrogen using electricity from renewable sources is an energy intensive process. New technologies like the one developed by UCSC can remove this barrier to large-scale adoption of hydrogen fuel.