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Sustainable Energy

Faster Catalysts Improve Hydrogen Generation

Researchers describe progress on technology for storing energy in the form of hydrogen fuel.

Anyone relying entirely on solar power or wind for electricity–say, in a remote location cut off from the grid–could use a cheap way to store power for use at night or when the wind isn’t blowing. Today at the American Chemical Society meeting in Boston, researchers announced progress on one option: using electricity from solar panels or other sources to split water, producing hydrogen fuel that can be used to produce electricity anytime by means of a fuel cell or generator.

Water Splitter: Daniel Nocera watches an apparatus that makes hydrogen and oxygen from water.

The researchers, led by MIT chemistry professor Daniel Nocera, say they’ve improved a system that uses potentially low-cost catalysts to facilitate a reaction in which electricity is used to break down water into hydrogen and oxygen, a process called electrolysis. Nocera says the catalysts could reduce the price of commercial electrolyzers to levels that are approximately 25 to 60 percent less than conventional electrolyzers and also make them practical for small-scale applications such as use in homes.

Nocera’s work is part of an effort to mimic photosynthesis, the process by which plants convert sunlight into useful molecules. Using electrons to split water is a key step in artificial photosynthesis, and Nocera is attempting to commercialize this water-splitting step through Sun Catalytix, a startup he founded in Cambridge, MA. The reaction can be powered with electricity from any source.

Water-splitting reactions involve depositing separate catalysts on two electrodes. One catalyst facilitates hydrogen production; the other facilitates oxygen production, the most challenging part of the process and the one that limits its rate. Nocera first announced new oxygen-producing catalysts in 2008, but they didn’t work very fast. Now, he says, they generate oxygen 200 times faster. The key is that his system now deposits the catalyst on a porous electrode, increasing the amount of catalyst in a given area. But the speed must increase 10 times to equal rates seen in commercial electrolyzers.

Whereas the catalysts used in commercial electrolyzers require acidic or highly alkaline solutions Nocera’s can function in ordinary neutral water. Nocera says the catalysts can even work with water taken directly from rivers or the ocean, making them more consumer friendly and practical for small applications. He envisions a small $30 electrolyzer being linked to solar panels and a fuel cell or generator in parts of poor countries where there’s no access to the electrical grid. In such settings, he says, the ability to use local water from rivers or the ocean would be a particular advantage, since pure water might be unavailable.

At this point, all cost figures are estimates: Sun Catalytix hasn’t yet brought a product to market. John Turner, a research fellow at the National Renewable Energy Laboratory in Golden, CO, says that Nocera’s results are promising, but “many questions remain.” For example, although initial tests show that the catalysts work with river water or seawater, the researchers haven’t determined how long they’ll last under those circumstances. “He’s got a long way to go to show a commercial device,” Turner says.

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