"The field was slow to pick up on this," Nocera added. "But we followed Turner's lead, and with the development of new catalysts — and by following Turner's approach — we were able to develop a buried junction comprising earth-abundant materials."

The Longer and Shorter Visions for Hydrogen

NREL intern Andrew Pinkard works on a photoelectrochemical characterization test to determine flat band potential in electrodes at NREL's hydrogen lab. Behind him is fellow intern Adolfredo Alvarez. Credit: Dennis Schroeder

Turner envisions a day when the United States and other nations depend by and large on domestically produced hydrogen as an energy carrier for transportation, heat, and electricity. No pollution, no dependency on foreign oil, no national security worries.

"In my view, a hydrogen economy is inevitable," Turner said. "Simply because we can't run on fossil fuels forever, and hydrogen makes the most sense when it comes to building a sustainable infrastructure." Turner says the two big visions for the hydrogen economy are its use in fuel cell vehicles and in producing ammonia, which is essential for food production.

"I'm talking about a system that will last for millennia."

Neale and Ruddy take a shorter-term view. They can envision solar-powered water splitting replacing reforming natural gas as the way refineries produce the hydrogen that is used to remove sulfur from petroleum or to convert heavy crude into lighter, easier-to-refine products.

If all the hydrogen were pulled out of a gallon of water, that amount of hydrogen would have 40% of the energy equivalence of one gallon of gasoline.

One challenge is the amount of solar cells needed to generate as much hydrogen fuel each day as a typical large oil refinery does. "You might need a few square miles of solar arrays around the refinery," Neale said.

Another hurdle is to show that the process will work as well when it is boosted to manufacturing scale. Recent NREL analysis indicates a path to getting a gallium-arsenide-based solar cell down to about $2 per watt. Using that as the base for the Turner water-splitting device would produce hydrogen at about $3 per kilogram. That would make it fairly competitive with gasoline. A kilogram of hydrogen can propel a car almost three times farther than a gallon of gasoline, but because hydrogen is so light, a vehicle's gasoline tank would provide a greater range than a vehicle's hydrogen tank.

Solar Power for the Long Run

Millions of middle-school students have done the basic experiment: Use an electric source and clamps to electrolyze water and watch the bubbles of hydrogen climb to the surface.

Using the sun and a solar cell eliminates the need for electrolyzers, or anything else that needs a fossil-fuel source.

"This has been languishing in the weeds, and now all of a sudden it's in the forefront," Turner said. "Our funding has been zeroed out twice, but in the past few years we've seen more interest." In fact, Turner already has given 23 invited talks on hydrogen in 2012, a personal record for talks in a year.

"I'm optimistic — if people will focus on the right concepts," Turner said. "That's what's necessary to make this field viable. It's going to take a new material, and people haven't been interested in looking at new materials. Now they are."

Of course, there are other pathways to produce hydrogen, including using biomass or algae, or extracting hydrogen using extreme heat. "The one that has the lowest cost for the hydrogen is the one that will prevail," Turner said.

NREL has a hydrogen filling station at its National Wind Technology Center, the stored hydrogen coming from solar- and wind-powered water splitting. And NREL houses the data repository for DOE's technology validation project on the performance of fuel cell vehicles.

On Track to Being a Scientist Early

Turner was sure of his future career when he was 12 and first saw the word "scientist" written on a blackboard in his Idaho elementary school.

"I saw the word, and I knew that was me," he said. "I came home and told my mom I was going to be a scientist. She said, 'That's cute, Johnny. Tomorrow you'll want to be a fireman.'

"But it never changed. In high school I took calculus, chemistry, physics, and biology, and decided on chemistry."

And he was fast enough in the 100- and 200-yard sprints and adept enough in the hurdles and triple jump to make sure his passion saw fruit.

He won a track scholarship to Idaho State University, got his Ph.D. in chemistry from Colorado State University, and did post-graduate work at Caltech — now the site of the big DOE Energy Innovation Hub on hydrogen.

Water and the Sun: For the Long Haul

Turner was a celebrity for a short while in 1998. His paper on using the sun for water splitting even inspired a film starring Keanu Reeves titled "Chain Reaction" about a hydrogen-fueled economy being the Earth's last best hope.

"We need a chemical energy carrier like gasoline, petroleum, methane, that carries energy in chemical bonds," Turner said. "It's all stored sunlight. That's what hydrogen represents."

Turner has some greats in science and literature on his side.

In Jules Verne's 1874 novel "Mysterious Island," a protagonist says: "Yes, my friends, I believe that water will someday be employed as fuel, that hydrogen and oxygen which constitute it … will furnish an inexhaustible source of heat and light … Someday water will be the coal of the future."

And in 1931, shortly before he died, Thomas Edison told his friends Henry Ford and Harvey Firestone: "I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that."

Turner puts it this way: "How much coal will we have in 75 years or 200 years? We have enough coal for ourselves and our kids, but what about our grandkids and great-grandkids? The sun and the wind are intermittent resources. We'll run out of fossil fuels. But the sun and water will be around for a long, long time."