Is MIT's Latest Solar 'Breakthrough' All Hype or a New Hope?

• MIT
• solar power
• alternative energy
• hydrogen

MIT announced on Thursday afternoon a new method of splitting water into hydrogen and oxygen, predicting that it will unleash a "solar revolution." And they're partly right. The research, which appears in the new issue Science, has little to do with solar power as we usually think of it. But it has wide-reaching implications as a storage medium, making renewable but intermittent energy sources like the sun and wind more practical for everyday use.

The work, by MIT professor Daniel Nocera and his postdoc Matthew Kanan, follows several decades of work in a field sometimes known as "artificial photosynthesis," because it attempts to mimic one of nature's best tricks—storing energy in chemical bonds. In this case, energy from the sun can be stored in hydrogen when it is split from water; Nocera and Kanan have developed a catalyst for doing that more cheaply and efficiently.

The news is perfectly timed to catch a wave of enthusiasm for all things solar, as a number of different sun-powered technologies are finally approaching maturity as scalable and cost-effective options. Companies like First Solar have succeeded in bringing second-generation, silicon-free solar panels to the market at half the cost of traditional silicon panels, and the first in a wave of utility-scale plants for solar-thermal energy went online outside Las Vegas last year. MIT itself is so excited about solar power that it has announced no less than three solar revolutions in the last six weeks, starting with "the most cost-efficient solar-power system in the world" on June 18, and adding "a new approach to harnessing the sun's energy" on July 10.

But in many ways, today's announcement isn't the latest in a string of solar breakthroughs—it's actually a piece of good news for boosters of the much-maligned "hydrogen economy." With Honda ramping up production of its FCX Clarity fuel-cell car and GM testing a fleet of its Chevy Equinox prototype, it's clear that hydrogen still has plenty of potential as a fuel-storage medium. Nocera's catalyst raises hopes—if not hype—that everyone with a roof could someday have a simple way of making hydrogen from water.

How It Works

Water is H2O—two hydrogen atoms and an oxygen atom—and scientists have known for two centuries how to apply a jolt of electricity to split it into hydrogen and oxygen, a process called electrolysis. What Nocera's scheme promises is a way of doing what existing commercial electrolyzers do, but much more simply and efficiently.

"Conceptually, it's the same thing," Nocera says. "But instead of feeding electrons into a hermetically sealed box filled with a concentrated base, we can feed them to an electrode sitting in a simple glass of water, at room temperature and pressure, with neutral pH." That simple setup makes it easy to build, operate and maintain.

Just as importantly, the catalyst identified by Nocera and Kanan uses cheap and abundant materials—cobalt and phosphorous—instead of the rare and expensive metals used as catalysts in existing systems. That's crucial, since the question isn't whether we can split water (we already know we can), but whether we can do it cheaply enough to install a system in every house.

The new catalyst actually facilitates the production of the oxygen byproduct. That's half the battle—a separate catalyst for hydrogen production is the other half—but it's crucial to making the whole process work. "You can't complete the circuit unless both parts are working," explains Tom Mallouk, a Penn State chemistry professor pursuing similar goals.

The search for a cheap, efficient oxygen catalyst has lagged far behind the development of hydrogen catalysts, according to University of California­Irvine professor Alan Heyduk, who worked with Nocera as a graduate student but wasn't involved in the current research. "This has been a bit of a holy grail," he says.

Mallouk agrees: "My group has been working on this as well, but so far we have been using relatively expensive elements to make it work. That's fine for proof-of-concept, but not much use in the real world."

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