The elusive dream of producing clean, inexhaustible fuel to run everything from our cars to our cell phones may not be quite as illusive as we had thought. Scientists around the world are making significant progress toward using sunlight to split water into hydrogen and oxygen.
The goal is alluring because a cheap way to extract hydrogen from water would end energy shortages around the world while cleaning up the environment using two of nature's gifts, water and sunlight.
Sound too good to be true? Maybe it is, because the challenges are still great, but there are several reasons to be optimistic. Within the past few days, several research teams have reported progress toward reducing the cost of hydrogen production, currently a show stopper.
Meanwhile, other teams are having some success in creating new materials that can trap and hold those tiny hydrogen atoms until they are ready to be used.
The competition is intense, for obvious reasons. We are still in the age of hydrocarbon fuels, because they have been easy to acquire and amazingly efficient in terms of the amount of potential energy in a given volume. It takes a lot of hydrogen to produce the same amount of useable energy as a gallon of gasoline, which, incidentally, has become extremely tough competition. But clearly oil is not inexhaustible, and those countries that have it can hold the rest of the world hostage. Something has to change.
Here are a few givens if hydrogen is to succeed. The cost of producing it must be slashed. More efficient ways to harness solar energy must be found, because sunlight is a critical component in any feasible large-scale method of splitting water. Hydrogen, like any other fuel, has safety risks that must be overcome.
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Yet hydrogen is being "aggressively explored" as a fuel for passenger cars, according to the Department of Energy, partly because it "has the potential to dramatically reduce our dependence on imported oil." It also could help in the fight against global warming because no greenhouse gases would need to be released into the atmosphere.
DOE is funding much of the research in this country, and it has set goals that some had thought could not be reached. Eight research institutions are trying to meet DOE's target of bringing the cost of hydrogen production down to $6 per kilogram (2.2 pounds) by 2015 and $2-$3 per kilogram by 2025. So far, only one team has reached those goals, the University of Colorado at Boulder.
The Boulder team built an array of mirrors to concentrate the sun's rays and generate temperatures as high as 2,640 degrees Fahrenheit. That heat, directed on a thin film of metal ferrite created by the Boulder team, splits water at 482 degrees cooler than other technologies.
In announcing the development, Alan Weimer of Boulder's chemical and biological engineering department, said the lower temperature makes water-splitting more cost effective and faster.
"It's pretty significant and it seems like there's a good shot for this to become mainstream in the southwest U.S. and other high isolation regions around the world," Weimer said.
Within days of that announcement several researchers reported progress in overcoming one of the main barriers to cost-effective production of hydrogen. Commercial hydrogen production today requires the use of platinum as a catalyst, which now sells for about $18,000 an ounce.
Is a Hydrogen Car in Your Future?
That's a show stopper for widespread use, and there isn't enough platinum in the world to produce enough hydrogen to power very many cars.
One team, at Australia's Monash University, discovered that birnessite, a common mineral that produces a black stain on rocks, also works as a catalyst for splitting water into hydrogen and oxygen. It mimics the way plants split water into fuel for growth, suggesting that there may be even more effective -- and cheaper -- substitutes for platinum.
Scientists at Stanford University are following a similar course. They are studying natural catalysts used by plants and other organisms to produce fuel for growth, and it looks like a common compound, molybdenum sulfide, might be "an inexpensive solution" for catalyzing hydrogen production, the researchers reported earlier this month. However, a different catalyst must be found to isolate the other component of water -- oxygen -- and the team is experimenting with other prospects. Left free to roam, oxygen will clog the chemical solar cell that powers the system.
Following a different course, scientists at Los Alamos National Laboratory have had some success experimenting with a compound of carbon, iron and cobalt as a catalyst.
But even if the cheap production of hydrogen is closer, how do you tame the stuff once you've got it? Hydrogen is the smallest atom, and thus it can squeeze in and out of every pore. You could use it today to run the family car, but it would seep past every hose clamp, and don't even think of keeping it in an ordinary gas tank. What is needed is some kind of matrix that is capable of holding a lot of hydrogen in a small place.
The hurdle here is to create seemingly solid stuff that has room for hydrogen. Rice University scientists say they have found that a class of material known as metallacarborane can store hydrogen better than the benchmarks set by DOE's hydrogen program for 2015. Other researchers at the University of California, Los Angeles, claim to have already solved the storage problem with a brand new material that works something like a sponge.
So if all of this pans out, is a hydrogen car in your future? It looks more likely now than it did just a couple of years ago. But success is not guaranteed. There's no way to distribute it like gasoline, but it seems reasonable that such an infrastructure would evolve fairly quickly if the potential is as great as so many scientists believe. However, there's a little problem with the competition.
Gasoline and diesel engines are getting better and better. So are batteries, leading to widespread acceptance of hybrids and electric vehicles. And sticker shock at the local hydrogen car dealership is likely to be awful as a brand new technology weaves its way through the marketplace.
So it's not going to happen tomorrow. But much progress is being made.