UCSC chemists develop gallium-aluminum composite for rapid generation of hydrogen under ambient conditions
22 February 2022
UC Santa Cruz chemists have developed a simple method to make aluminum nanoparticles that split water and generate hydrogen gas rapidly under ambient conditions. The water-splitting reaction does not require an applied potential and functions at ambient conditions and neutral pH to rapidly generate 130 mL (5.4 mmol) of hydrogen per gram of alloy. A paper on their work is published in the journal ACS Applied Nano Materials.
Aluminum is a highly reactive metal that can strip oxygen from water molecules to generate hydrogen gas. Its widespread use in products that get wet poses no danger because aluminum instantly reacts with air to acquire a coating of aluminum oxide, which blocks further reactions.
For years, researchers have tried to find efficient and cost-effective ways to use aluminum’s reactivity to generate clean hydrogen fuel. A new study by the researchers at UCSC shows that an easily produced composite of gallium and aluminum creates aluminum nanoparticles that react rapidly with water at room temperature to yield large amounts of hydrogen. The gallium was easily recovered for reuse after the reaction, which yields 90% of the hydrogen that could theoretically be produced from reaction of all the aluminum in the composite.
We don’t need any energy input, and it bubbles hydrogen like crazy. I’ve never seen anything like it.—UCSC Chemistry Professor Scott Oliver, co-corresponding author
Bubbles of hydrogen gas are generated from the reaction of water with an aluminum-gallium composite. Movies of the reaction are available online. (Credit: Amberchan et al., Applied Nano Materials 2022)
The reaction of aluminum and gallium with water has been known since the 1970s, and videos of it are easy to find online. It works because gallium, a liquid at just above room temperature, removes the passive aluminum oxide coating, allowing direct contact of aluminum with water. The new study, however, includes several innovations and novel findings that could lead to practical applications.
A US patent application is pending on this technology. The international (PCT) filing on which it was based is here.
Previous studies had mostly used aluminum-rich mixtures of aluminum and gallium, or in some cases more complex alloys. But the lab of Bakthan Singaram, professor of chemistry and biochemistry and co-corresponding author of the study, found that hydrogen production increased with a gallium-rich composite. In fact, the rate of hydrogen production was so unexpectedly high the researchers thought there must be something fundamentally different about this gallium-rich alloy.
Oliver suggested that the formation of aluminum nanoparticles could account for the increased hydrogen production, and his lab had the equipment needed for nanoscale characterization of the alloy. Using scanning electron microscopy and x-ray diffraction, the researchers showed the formation of aluminum nanoparticles in a 3:1 gallium-aluminum composite, which they found to be the optimal ratio for hydrogen production.
Scanning electron microscopy of the composite shows aluminum nanoparticles in a matrix of gallium. (Credit: Amberchan et al., Applied Nano Materials 2022)
In this gallium-rich composite, the gallium serves both to dissolve the aluminum oxide coating and to separate the aluminum into nanoparticles.
Making the composite required nothing more than simple manual mixing. The composite can be made with readily available sources of aluminum, including used foil or cans, and the composite can be stored for long periods by covering it with cyclohexane to protect it from moisture.
Although gallium is not abundant and is relatively expensive, it can be recovered and reused multiple times without losing effectiveness, Singaram said. It remains to be seen, however, if this process can be scaled up to be practical for commercial hydrogen production.
This work was partially supported by funds from the Ima Hernandez Foundation.
Gabriella Amberchan, Isai Lopez, Beatriz Ehlke, Jeremy Barnett, Neo Y. Bao, A’Lester Allen, Bakthan Singaram, and Scott R. J. Oliver (2022) “Aluminum Nanoparticles from a Ga–Al Composite for Water Splitting and Hydrogen Generation” ACS Applied Nano Materials doi: 10.1021/acsanm.1c04331
Nice science experiment. They don't talk about the electrical energy required recycle the aluminum oxide, or the CO and CO2 generated when the by the carbon electrodes consumed in the process. They also don't talk about round trip efficacy.
Posted by: TimFlavin1 | 22 February 2022 at 06:23 AM
This reminds me of the “Mr Fusion” on the back of the Delorian. Pure the beer in and then throw the can in, close the reactor and fly away!
Posted by: Tim Duncan | 22 February 2022 at 01:12 PM
What carbon electrodes are you referring to? This is not a process involving electrolysis. Reread the article.
Posted by: Paroway | 22 February 2022 at 06:17 PM
"We don’t need any energy input, and it bubbles hydrogen like crazy. I’ve never seen anything like it." What BS. They already put the energy in by converting aluminum oxide to aluminum which is quite energy intensive. There are a a number of other metals they could more easily use that do not require gallium. Just drop sodium (or potassium or lithium) into water. Instant hydrogen. I ran an physics experiment once that used potassium. I needed to clean up the equipment after running the experiment. Filled an industrial sink with water. Stood a few feet back and tossed the equipment into the sink. Boom! Instantly clean.
@Paroway The carbon electrodes are used in making the aluminum. See https://en.wikipedia.org/wiki/Hall%E2%80%93H%C3%A9roult_process
Posted by: sd | 22 February 2022 at 06:57 PM
The carbon electrodes are used to refine the aluminum in the first place. A careful reading of the article also indicates that the aluminum is turned into aluminum oxide. This also requires the same refining step to turn the aluminum oxide back into aluminum. My point was that they were ignoring the fact that creating aluminum requires a lot of energy and has its own CO2 problem. Nice lab experiment but if you are looking for a green solution this only solves a tiny part of the problem.
Posted by: TimFlavin1 | 23 February 2022 at 07:07 AM
Aluminum oxidizes in air. No energy input is needed. They are using scrap aluminum. Cans, parts or what ever. The aluminum they use already exists, and millions of tons are thrown in waste sites annually.
The aluminum oxide is removed from the aluminum by the reaction of the gallium aluminum alloy in water at room temperature.
Posted by: Paroway | 25 February 2022 at 05:12 PM