Cheap Catalyst Could Turn Sunlight, Water Into Fuel
By Alexis Madrigal
A new catalyst makes it feasible to split water with solar power.
MIT chemists say the catalyst, used in conjunction with cheap photovoltaic solar panels, could lead to inexpensive, simple systems that use water to store the energy from sunlight.
In the process, the scientists may have cleared the major roadblock on the long road to fossil fuel independence: Reducing the on-again, off-again nature of many renewable power sources.
The catalyst enables the electrolysis system to function efficiently at room temperature and at ordinary pressure. Like a reverse fuel cell, it splits water into oxygen and hydrogen. By recombining the molecules with a standard fuel cell, the O2 and H2 could then be used to generate energy on demand.
"You've made your house into a fuel station," Daniel Nocera, a chemistry professor at MIT said. "I've gotten rid of all the goddamn grids."
Solar energy currently makes less than one percent of the world's electricity. The main drawback of the technology, preventing wider adoption, is that solar systems only make power while the sun is shining. At night or on cloudy days, those in need of power must look elsewhere. So storage of electrical energy has been a long-sought after technological advance. Batteries work but they're too big and expensive. Fuels, fossil or renewable, are different: They act as their own storage, allowing for easy transport and usage. That's one reason that coal and oil have such a dominant hold on the world's energy market.
The MIT discovery could help transform electricity generated through solar energy into a fuel, making it more competitive with fossil fuels. That could prove to be a major milestone in clean technology.
"I think it's a very interesting discovery," said Tom Mallouk, a chemistry professor at Penn State. "It's one of those papers that really has the potential to change the field."
The key advancement in Nocera's Science paper is the development of an oxygen-producing catalyst made of cobalt and phosphate. Splitting water requires two half-reactions, one to create oxygen gas and the next to create hydrogen. For decades, Mallouk said, scientists have been trying to reduce the cost of the oxygen part of the reaction, with little success.
"The hydrogen side of the cell is only two electrons per molecule. The oxygen side is four electrons per molecule," Mallouk said. "There is a rule in electrochemistry that the more electrons you have the more complicated the process is."
It's important to note that Nocera's breakthrough is in making it cheaper and simpler to split water by electrolysis. Expensive machines have long been able to do the same thing, but only by using iridium alloys or exotic nanoparticles.
The new catalyst is remarkable because its made of common materials and can operate at room temperature and normal pressure. Without the need to heat and pressurize the water, the energy needs and cost of running the process overall are much lower. And that could make a standard solar array on a home a viable source of electricity for creating all the hydrogen a household would need.
The joke in clean tech circles about hydrogen is that "hydrogen is the fuel of the future and always will be." But that's in large part because producing hydrogen has been so expensive and energy-intensive to produce. Most of the power in the world comes from fossil fuel, too, so making hydrogen generated tons of greenhouse gases.
"It's never an issue in energy of whether you can do it or not," Nocera said. "It's whether you can do it cheaply."
And whether or not the setup will prove cost-effective remains to be seen. It still uses a platinum catalyst to produce hydrogen, for example.
Erik Straser, a leading clean technology investor with the venture capital firm, Mohr-Davidow, termed the technology "promising," but said the new paper didn't shed light on its economic viability.
"I think that having operation at room temp and standard pressure is a key innovation," he wrote in an e-mail to Wired.com. "What is not there are any of the metrics that would let you determine whether this made economic sense (a huge issue in these energy technologies)."
Other scientists are, however, hard at work trying to find cheaper hydrogen producing catalysts, including a group of scientists led by Bjorn Winther-Jensen who published work on a carbon-based catalyst in the same issue of Science this week.
Nocera himself admits that he hasn't "driven down the whole road" on what the setup could cost. And, solar panels remain very expensive on a per-kilowatt basis, even as innovation in the field continues to drive costs down for consumers.
Still, despite the questions about the commercial viability of the technology, Nocera said that the Bob Metcalfe-run venture capital firm, Polaris, had "swooped in" on the technology and was filing for patent protections.
Though Nocera doesn't expect retail systems to be available for the better part of a decade, the questions about the viability of his idea should begin to be answered soon, as prototype designs attempt to deliver on his big promises.
"Within two years, you'll start seeing module designs," Nocera said. "A lot of my MIT colleagues are raring to go and work on this and they are all engineers and they're pretty damn good."