Easy aluminum nanoparticles for fast and efficient generation of hydrogen from water


Aluminum is a highly reactive metal that can extract oxygen from water molecules to generate hydrogen gas. Its widespread use in products that get wet presents no danger because aluminum reacts instantly with air to acquire a layer of aluminum oxide, which blocks further reactions.

For years, researchers have tried to find efficient and cost-effective ways to use the reactivity of aluminum to generate clean hydrogen. A new study by researchers at the University of California, Santa Cruz (UCSC) shows that an easily produced gallium-aluminum composite creates aluminum nanoparticles that quickly react with water at room temperature to produce large amounts of hydrogen. The gallium was easily recovered for reuse after the reaction, yielding 90% of the hydrogen that could theoretically be produced from reacting all the aluminum in the composite.

“We don’t need any energy input, and the hydrogen is bubbling like crazy. I’ve never seen anything like it,” said UCSC chemistry professor Scott Oliver.

Oliver and Bakthan Singaram, professor of chemistry and biochemistry, are the corresponding authors of an article on new discoveriesPosted in Nano materials applied.

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 just above room temperature, strips the passive coating of aluminum oxide, allowing direct contact of aluminum with water. The new study, however, includes several innovations and new findings that could lead to practical applications.

A US patent application is pending on this technology.

Singaram said the study grew out of a conversation he had with a student, co-author Isai Lopez, who had seen videos and started experimenting with aluminum-gallium hydrogen generation in his kitchen.

“He wasn’t doing it in a scientific way, so I put him in touch with a graduate student to do a systematic study. I thought it would make a good thesis for him to measure hydrogen production from different ratios of gallium and aluminum,” Singaram said.

Previous studies had mainly used mixtures of aluminum and aluminum-rich gallium, or in some cases more complex alloys. But the Singaram lab found that hydrogen production increased with a gallium-rich composite. In fact, the rate of hydrogen production was so surprisingly high that 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 to perform the 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. .

In this gallium-rich composite, the gallium serves both to dissolve the aluminum oxide coating and to separate the aluminum into nanoparticles. “The gallium separates the nanoparticles and prevents them from aggregating into larger particles,” Singaram said. “People have struggled to make aluminum nanoparticles, and here we produce them under normal atmospheric pressure and room temperature conditions.”

Making the composite required nothing more than simple hand mixing.

“Our method uses a small amount of aluminum, which ensures that everything dissolves in the majority of the gallium as discrete nanoparticles,” Oliver said. “This generates a much larger amount of hydrogen, almost complete compared to the theoretical value based on the amount of aluminum. It also facilitates the recovery of gallium for reuse.

The composite can be made with readily available aluminum sources, including used foil or cans, and the composite can be stored for long periods of time by covering it with cyclohexane to protect it from moisture.

Although gallium is not abundant and is relatively expensive, it can be collected and reused many 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.

First author Gabriella Amberchan is a graduate student in the Singaram lab. Other co-authors on the paper include Beatriz Ehlke, Jeremy Barnett, Neo Bao, and A’Lester Allen, all at UCSC. This work was partially supported by funds from the Ima Hernandez Foundation.

– This press release was originally published on the University of California – Santa Cruz website


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