Hydrogen Fuel On Demand With Silicon Nanoparticles | Chemical & Engineering News
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Web Date: January 24, 2013

Hydrogen Fuel On Demand With Silicon Nanoparticles

Fuel Cells: The nanomaterials could generate hydrogen in portable fuel cells to power portable electronics
Department: Science & Technology | Collection: Sustainability
News Channels: Materials SCENE, Nano SCENE, Environmental SCENE
Keywords: energy storage, hydrogen fuel, nanomaterials, fuel cell, silicon
Silicon particles 10 nm in diameter react rapidly with water to produce hydrogen.
Credit: Swihart Lab, University of Buffalo
Silicon particles 10 nm in diameter react rapidly with water to produce hydrogen.
Credit: Swihart Lab, University of Buffalo

Hydrogen fuel cells produce electricity without harmful emissions, but the devices face a significant hurdle to widespread use: Transporting the flammable fuel poses safety risks. So scientists have been working on systems for making the fuel where it’s needed, by splitting water into hydrogen and oxygen gas. Now researchers report that silicon nanoparticles could help. The nanoparticles react with water to produce hydrogen much faster than larger forms of silicon can (Nano Lett., DOI: 10.1021/nl304680w).

Some prototype hydrogen-generating systems use metal materials such as magnesium hydride, aluminum, or zinc to react with water. The compounds don’t require light, catalysts, or heat to push the reactions along. But these materials often react slowly, which isn’t ideal for applications that need a quick burst of electrical power.

Paras N. Prasad and Mark T. Swihart, of the University at Buffalo, wanted to test whether silicon nanoparticles might perform better. They knew that bulk silicon reacted slowly with water to produce hydrogen and that, as the reaction proceeds, oxides form on the silicon surface, halting the reaction. But the chemists and their colleagues thought the high surface-area-to-volume ratio of silicon in nanoparticle form would lead to speedy reaction rates.

The team studied the reaction of slightly basic water with three types of roughly spherical silicon particles: 10-nm-diameter particles made in their lab along with commercially available 100-nm and 40-µm ones. The smallest particles are surprisingly fast, the scientists report. The 10-nm particles produce 1 mmol of hydrogen in five seconds, while the 100-nm and 40-µm ones take 811 and 3,075 seconds, respectively. The reaction rate for the 10-nm particles was six times quicker than that of aluminum and zinc nanoparticles, the previous fastest rates reported in the literature, Swihart says.

The Buffalo group then tested the particles in a hydrogen fuel cell loaded with water, to ensure that the reactions produce hydrogen without creating any side products that could damage the fuel cell. During a small test, a nanoparticle-water mix generated enough hydrogen to run a commercial fuel cell for about four minutes. The cell ran normally, as it would if fed pure hydrogen, with no apparent damage.

However, John Turner, a research fellow who specializes in hydrogen fuel cells at the National Renewable Energy Laboratory in Golden, Colorado, is not convinced that nanosilicon is a good means to generate hydrogen, especially if the goal is to produce electricity with low emissions. Prasad’s group makes the nanoparticles from silane gas, and producing the gas, Turner says, requires a lot of energy and generates carbon dioxide. “You have to take a holistic look at the energy that goes into the whole process.”

Prasad says his group plans to address these practical issues after further basic research into how conditions such as particle shape affect the silicon-water reaction.

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Chris King  (January 28, 2013 11:19 AM)
Before C&E News publishes any more articles on fuel cells and the like, it should make sure to include an (holistic) energy balance, as indicated by John Turner of NREL. Without this the articles are just incomplete, and just journalistic hype.
Raul  (February 1, 2013 12:55 PM)
Congratulations to the researchers Paras and Mark, I am sure that this kind of research will bring a lot of progress for people and it will be a significant step on transforming world energy sources and many other technologies such as transport, industry and home utilities, and of course hope it will be frendly to environment.
Shaukat Ismail  (May 27, 2013 5:44 AM)
Thank u very much but not mention 1 litter how many gram use and one liter how many gas cm3 produce
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