MIT: A Big Leap for an Artificial Leaf: Making Liquid Fuel from Sunlight, Water and CO2: Video


A cross-disciplinary team at Harvard University has created a system that uses solar energy to split water molecules and hydrogen-eating bacteria to produce liquid fuels. The system can convert solar energy to biomass with 10 percent efficiency, far above the one percent seen in the fastest-growing plants.

 

The bionic leaf is one step closer to reality.

Daniel Nocera, a professor of energy science at Harvard who pioneered the use of artificial photosynthesis, says that he and his colleague Pamela Silver have devised a system that completes the process of making liquid fuel from sunlight, carbon dioxide, and water. And they’ve done it at an efficiency of 10 percent, using pure carbon dioxide—in other words, one-tenth of the energy in sunlight is captured and turned into fuel.

That is much higher than natural photosynthesis, which converts about 1 percent of solar energy into the carbohydrates used by plants, and it could be a milestone in the shift away from fossil fuels. The new system is described in a new paper in Science.

 

 
“Bill Gates has said that to solve our energy problems, someday we need to do what photosynthesis does, and that someday we might be able to do it even more efficiently than plants,” says Nocera. “That someday has arrived.”Artificial Photosynth ext

 

 
In nature, plants use sunlight to make carbohydrates from carbon dioxide and water. Artificial photosynthesis seeks to use the same inputs—solar energy, water, and carbon dioxide—to produce energy-dense liquid fuels. Nocera and Silver’s system uses a pair of catalysts to split water into oxygen and hydrogen, and feeds the hydrogen to bacteria along with carbon dioxide.

 

 

The bacteria, a microörganism that has been bioengineered to specific characteristics, converts the carbon dioxide and hydrogen into liquid fuels.

 

 
Several companies, including Joule Unlimited and LanzaTech, are working to produce biofuels from carbon dioxide and hydrogen, but they use bacteria that consume carbon monoxide or carbon dioxide, rather than hydrogen. Nocera’s system, he says, can operate at lower temperatures, higher efficiency, and lower costs.

 

 
Nocera’s latest work “is really quite amazing,” says Peidong Yang of the University of California, Berkeley. Yang has developed a similar system with much lower efficiency. “The high performance of this system is unparalleled” in any other artificial photosynthesis system reported to date, he says.

 

 
The new system can use pure carbon dioxide in gas form, or carbon dioxide captured from the air—which means it could be carbon-neutral, introducing no additional greenhouse gases into the atmosphere. “The 10 percent number, that’s using pure CO2,” says Nocera. Allowing the bacteria themselves to capture carbon dioxide from the air, he adds, results in an efficiency of 3 to 4 percent—still significantly higher than natural photosynthesis.

 

 

“That’s the power of biology: these bioörganisms have natural CO2 concentration mechanisms.”

 

 
Nocera’s research is distinct from the work being carried out by the Joint Center for Artificial Photosynthesis, a U.S. Department of Energy-funded program that seeks to use inorganic catalysts, rather than bacteria, to convert hydrogen and carbon dioxide to liquid fuel.

 

 

According to Dick Co, who heads the Solar Fuels Institute at Northwestern University, the innovation of the new system lies not only in its superior performance but also in its fusing of two usually separate fields: inorganic chemistry (to split water) and biology (to convert hydrogen and carbon dioxide into fuel). “What’s really exciting is the hybrid approach” to artificial photosynthesis, says Co. “It’s exciting to see chemists pairing with biologists to advance the field.”

 

 
Commercializing the technology will likely take years. In any case, the prospect of turning sunlight into liquid fuel suddenly looks a lot closer.

 

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MIT Professor: Power Your House With 5 Liters of Water Per Day – March 2009 – Where Are We Today?


MIT Solar Water Power splash

March 27, 2009 – At the Aspen Environment Forum today, MIT professor Dan Nocera gave a revolutionary picture of the new energy economy with an assertion that our homes will be our power plants and our fuel stations, powered by sunlight and water. And it’s not science fiction.

Nocera stated that even if we put all available acreage into fuel crops, all available acreage in wind power, and build a new nuclear power plant every 1.5 days, and we save 100% of our current energy use (yes, you read that correctly), we will still come up short by 2050. His estimate is that we will need 16 TW of energy production by then, and with our current methods, we won’t get there.

But there is a solution. And we don’t need to invent anything new to get from here to there.

Nocera said that MIT will announce its patent next week of a cheap, efficient, manufacturable electrolyzer made from cobalt and potassium phosphate. This technology, powered by a 6 meter by 5 meter photovoltaic array on the roof, is capable of powering an entire house’s power needs plus a fuel cell good for 500 km of travel, with just 5 liters of water.

The new electrolyzer works at room temperature (“It would work in this water glass right here”) to efficiently produce hydrogen and oxygen gases from water in a simple manner, which will enable a return to using sunlight for our primary energy source.

This technology will decentralize power production and provide true energy independence. The details of implementation still need to be worked out, but Nocera says that fears of hydrogen technology (safety) are unfounded, as companies that work with these gases have the capability to safely store and use them.  “It’s safer than natural gas. You burn that in your house with an open flame. Now that’s dangerous.”

*** Team GNT Writes: In 2009 – Professor Nocera’s announcement was, well … “stunning” to the Renewable Energy community to say the least. So what has become of Professor Nocera’s research?

Where Are We TODAY? – The Artificial Leaf

Prof D. Nocera df12556_79822

“Nocera’s critics—and there are many—want people to know that, in their view, the artificial leaf is virtually a nonstarter in today’s renewable energy landscape: The technology doesn’t plug into the existing power infrastructure (the “grid”), it’s not that cheap or efficient, and hydrogen as a fuel is no safer than other combustible fuels.

Mike Lyons, a chemist at Trinity College Dublin, Ireland, told Chemistry World magazine last year, “Dan’s a great story teller. But that has its inherent dangers.” Other critics point out that Nocera’s own start-up company, Sun Catalytix of Cambridge, Massachusetts, quietly shelved development of the artificial leaf technology a few years ago.

*** From a Special Report: National Geographic “Innovators” Series ***

As usual, Daniel Nocera came in by the back door.

On a rainy night in April, as the trees on the Boston College campus were sending out their first tentative shoots of spring, Nocera arrived (slightly late) as the keynote speaker for a meeting of the American Physical Society, where he was about to discuss a decidedly inorganic variation on a vernal theme: the “artificial leaf,” his invention that uses sunlight to generate an alternative form of energy.

Nocera made his way across a parking lot, went in the “Employees Only” entrance to the banquet hall, asked a bemused janitor for directions, and found himself in an elevator that deposited him right in the middle of the kitchen. “I’m the speaker tonight,” he told an equally bemused maître d’. “Do you know how to get there?”

“You’re in the right place,” the maître d’ announced. “Follow me!” And the man proceeded to lead Nocera out to the dining room.

“Whaddarewe having tonight?” Nocera asked in his rapid, exuberant New York patois, as he passed line cooks preparing roast beef, chicken, and vegetarian lasagna. Because he sees everything through the lens of photosynthesis, the meal becomes material for the talk he was about to give.

To save the planet from the dire consequences of its hydrocarbon addiction, we are going to have to overhaul our entire energy system.

Life on Earth has converted energy from the sun for at least three billion years, and the sun may be the answer to our energy needs in the future, he begins. He tells the audience that even the food they are starting to digest is unleashing energy from chemical bonds originally forged by the sun.

Nocera, 56, is a professor of energy at Harvard University, and a bit of a celebrity innovator in renewable energy circles, but he never forgets (and never lets you forget) that he has always taken the hard way, the less-traveled way, and certainly the less conventional way—from his second-grade excommunication from parochial school, to his defiant rejection of the immigrant values of his Italian American family, to his serial desertions from high school to follow his favorite rock band. It was almost inevitable that his scientific career would also follow a quixotic path.

Saving the Planet From Hydrocarbon Addiction

Nocera rarely passes up an opportunity to explain the artificial leaf. He estimates that he gave a hundred invited talks last year, and almost all the rubber-chicken sermons dwell on sustainability and renewable energy. Of all his provocative assertions, however, perhaps the most radical is not scientific but socioeconomic: To save the planet from the dire consequences of its hydrocarbon addiction, we are going to have to overhaul our entire energy system, and the only way to do that, he says, is to “take care of the poor.” They will be the early adopters of the artificial leaf, he believes, and they will lead the way to an era Nocera echoes Bryan Furnass in calling the “Sustainocene.”

It’s not a particularly popular, or even feasible, message at the moment, and the frequent talks are also a reminder that sometimes the hardest part of innovation comes after you make the discovery.

Daniel Nocera, a professor at Harvard University, is a bit of a celebrity innovator in renewable energy circles. PHOTOGRAPH BY DEANNE FITZMAURICE, NATIONAL GEOGRAPHIC

It takes a special temperament to want to be the kind of messenger that everyone wants to shoot; if not born to the part, Nocera has certainly warmed to the task. Mischievous child, rebellious teenager, long-haired counterculture scientist—they’re all on his resume. And although in photographs he projects an ascetic, almost clerically severe demeanor, he turns out in person to be a gregarious provocateur, charmingly pugnacious and as ebullient as the bubbles in the beaker of his most famous invention.

“Because I Was an American. I Had to Succeed.”

Nocera first became interested in science as a kind of buffer against the almost yearly relocations his family made—Massachusetts, Rhode Island, New York, New Jersey—to accommodate his father’s frequent work transfers (he was a retail buyer for Sears and later J. C. Penney). “The most defining point of my young life was when I was having breakfast one morning and I found out our house had been sold,” he says. “People ask, ‘Why did you become a scientist?’ Because when you’re waking up and you lose your friends every morning because you’re moving again, you start focusing on things you can control. I really turned to science because I could carry it with me.” The things he carried included a microscope and radio he built himself, assembled with the 1960s version of do-it-yourself science kit.

“In and Out” of School

One of his earliest experiments, alas, was throwing a “really chalky” eraser at a nun at his parochial school because he was curious to see what kind of mark it would leave on a black habit; the result was “spectacular,” but he was invited to leave. He embraced the rough-and-tumble of public schooling, even as he rejected his family. “I didn’t like my parents,” he says bluntly. “They always drove me so hard.” To get even, the teenaged Nocera became a member of an Orthodox synagogue in Tenafly, the northern New Jersey town where the family finally settled. “To annoy my Catholic mother,” he says, “I decided to join a temple. I became the best Jew.”

His academic career was spotty, too—he attended Bergenfield High School in northern New Jersey, but only intermittently (“in and out” is how he puts it). “I was the kid with the long hair that all the parents would tell all the other kids, ‘Stay away from him!'” By the time he was in high school, he started disappearing for weeks at a time to follow the Grateful Dead at concerts. “I really went to the Grateful Dead because I needed a family of people,” he says, “and the Grateful Dead is about family.” (The computer in his spare, corner office at Harvard contains 111 gigabytes of Grateful Dead music, to which he listens while writing scientific papers.)

I really turned to science because I could carry it with me.

Given that background, Nocera was not exactly a Westinghouse Science Talent Search kind of kid. He attended Rutgers University and initially planned to pursue biology, until everyone in his family told him he should be a doctor, at which point he switched to chemistry. After graduating in 1979, he entered the Ph.D. program at one of the world’s citadels of hard science: California Institute of Technology.

His adviser at Caltech, Harry Gray, had done pioneering work in photosynthesis, the process by which plants convert sunlight into usable energy. Alternative energy was much in the air because of the Arab oil embargo of the 1970s, and Nocera became captivated by the idea of using sunlight like a leaf does, to split water into hydrogen and oxygen. “I went to graduate school to do that,” he says, and spent the next 30 years trying to get the idea to work. But an innovative idea in energy, he learned, isn’t enough; the idea has to be cheap enough to compete “against the cold, hard facts of a real economic system.”

In 1995, a special issue of the journal Accounts of Chemical Research asked leading chemists to describe “holy grail” projects in the field; one of the essays, by Allen J. Bard and Marye Anne Fox, then at the University of Texas at Austin, described the process of splitting water using sunlight. The sheer simplicity of the process conceals its chemical elegance—it takes energy to break chemical bonds, such as the bonds that hold hydrogen atoms to oxygen in a molecule of water, and plants use the energy of sunlight to break those bonds. The result is hydrogen and oxygen. Plants release oxygen into the air and repurpose the hydrogen to make food, in the form of carbohydrates. But hydrogen on its own, as a gas, is a clean and storable form of energy known as a chemical fuel; it can be stored for later use, and that’s what Nocera was after.

Meet the Artificial Leaf

The idea is simple and elegant, but not easy and especially not easy without considerable cost. (John Turner of the National Renewable Energy Laboratory in Colorado had in fact achieved a version of water-splitting years earlier, but the process used prohibitively expensive materials.) Nocera began working on a cheap and simple approach during his grad school days at Caltech, continued after he took a job as a professor at Michigan State University in 1984, and finally declared success in a splashy 2011 paper in Science as a professor at Massachusetts Institute of Technology, where he moved in 1997.

Nocera’s artificial leaf can split oxygen from hydrogen—mimicking the natural process of plants. PHOTOGRAPH BY DEANNE FITZMAURICE, NATIONAL GEOGRAPHIC

What does an artificial leaf look like?

“We can go in the lab,” Nocera says, rising from his desk. “I’ll just turn on a fake sun, and we can look at it. I mean, right now! Just to prove how easy it is. And you’ll see, like, bubbles coming … smooooosh!” Snapping his fingers, he adds, “It will be that fast.”

In reality, the artificial leaf—at least the demonstration version a graduate student fetched out of a lab drawer—looks more like a sawed-off postage stamp than an appendage on any self-respecting tree. It’s not green; it’s not leaf-shaped; and it doesn’t convert water and carbon dioxide into carbohydrates, as plant leaves do. But after a few minutes of setup, the graduate student placed the “leaf” in a little beaker of water and focused light on it. Within moments, a steady stream of miniscule bubbles scrambled off the leaf, like a rat race of effervescence.

The leaf is actually a thin sandwich of inorganic materials that uses the energy of sunlight to break the chemical bonds holding hydrogen and oxygen atoms together in ordinary H2O. The leaf works because the middle of the sandwich is what’s called a photovoltaic wafer, which converts sunlight into wireless electricity, and that electricity is then channeled to the outer layer of the “leaf,” which is coated with different chemical catalysts on either side. One accelerates the formation of hydrogen gas, the other oxygen.

The artificial leaf mimics the natural process of photosynthesis. PHOTOGRAPH BY DEANNE FITZMAURICE, NATIONAL GEOGRAPHIC

Renewable Energy Celebrity

Armed with this basic invention, Nocera leaped ahead—too far and too fast, according to some of his critics—to a radical vision of how the artificial leaf would revolutionize the world. In a scenario he often shares in talks, he sees artificial leaves on the roof of every house, using sunlight to convert ordinary tap water into hydrogen and oxygen; the photovoltaic cells could provide electricity during daylight hours, and the hydrogen could be stored and later converted in a fuel cell to electricity overnight. Your house would become your personal power plant and your gas station, fueling the hydrogen-powered cars that Nocera says are already on the way. And, as he likes to say, “You can buy all this stuff on Google today.”

In 2011, when Nocera first described the artificial leaf at the annual meeting of the American Chemical Society, the immediate reaction was huge. MIT issued a big press release. Nocera formed a start-up company, Sun Catalytix, to commercialize the invention. There were YouTube videos; Nocera became a renewable energy go-to celebrity, invited to events like the Mountain Film Festival in Telluride, Colorado. And when he decided to move his research group to Harvard in 2012, online chemistry blogs dissected the transfer as if it were a superstar trade in baseball. “Nocera to Harvard!” ChemBark reported.

But not all the attention has been positive, not least because of the term “artificial leaf.” Many scientists thought it was a grandiose, attention-getting name. “Oh, they hate me!” Nocera confirms. “It’s like sport to come after me. But you can see with my retiring personality that it’s very upsetting to me,” he adds with a smile. Indeed, it brings out the combative public school persona in him. “It’s like being outside the boys’ room and getting into fights,” he says. “I did that a lot of times in my life, so I’m pretty good at this.”

“Frugal Innovation”

Despite the criticism, Nocera notes that the artificial leaf incorporates several key innovations. One is the discovery of a special kind of catalyst (created by then-lab member Matthew Kanan in 2008) that basically accelerates the formation of oxygen without depleting itself; in other words, the cobalt-phosphate coating on one side of the leaf acts as a middleman-facilitator to the chemical splitting of water without either using itself up or charging a minimal fee (in terms of energy). Another is that the basic architecture of the leaf is simple, modular, and relatively inexpensive, satisfying Nocera’s desire for what he calls “frugal innovation.”

Nocera wakes up every morning thinking about how to make the artificial leaf technology cheaper, more efficient, and simpler so that it will be impossible to resist the frugality of its innovation.

The company had “really tough discussions” in the fall of 2011, Nocera admits, about whether to proceed with a pilot project to test the artificial leaf idea in a developing country, and decided to “backburner” the technology until it could be done more cheaply. As Nocera puts it, “I did a holy grail of science. Great! That doesn’t mean I did a holy grail of technology. And that’s what scientists and professors don’t get.”

Sun Catalytix has shifted its focus to another technology—one that plugs into the existing infrastructure, but still advances the cause of renewable energy; it’s called a flow battery, and Nocera believes it will provide a cheap, innovative way to store energy on the grid. Meanwhile, Nocera insists, the company “has not given up on the artificial leaf” and still plans to field-test the idea, but only when the technology is less expensive. “So what are we talking about?” he says. “Innovation to reduce cost.”

A fuel cell can turn the split oxygen and hydrogen from the artifical leaf into energy. PHOTOGRAPH BY DEANNE FITZMAURICE, NATIONAL GEOGRAPHIC

Revolution in Renewable Energy

Nocera is a self-confessed workaholic. He says he works up to 14 hours a day, seven days a week, and he wakes up every morning thinking about how to make the artificial leaf technology cheaper, more efficient, and simpler so that it will be impossible to resist the frugality of its innovation.

But he’s also chastened by the challenge ahead. On the one hand, he sees a projected world population of nine billion people by 2050, who will need an estimated 30 terawatts—30 trillion watts—of energy; building 200 new nuclear power plants a year for 40 years, he tells the Boston College audience, wouldn’t satisfy the demand. On the other hand, traditional venture capitalism in the developed world doesn’t have the patience or vision, he says, to invest in the massive changes necessary to create an alternative energy system.

In the developed world, Nocera points out, venture capitalists want a return on their investment in two to five years—”and five is really generous,” he says. Setting up an alternative, photosynthetic-based energy system will never satisfy the appetite for a quick return on investment. “What’s the VC community good at?” he says. “An app that a kid can do in a college dorm—which many have done at Harvard. And it gives them their success stories, and makes them all rich. But these are apps. We’re not talking about high-end [innovation]. With energy, we’re talking about changing a massive infrastructure. There’s nothing a kid in his college room dorm is going to do that’s going to change a massive infrastructure.”

How massive? There’s no firm, agreed-upon figure on America’s historical investment in the current power infrastructure—the power plants, the coal mines, the oil rigs and fracking wells, the refineries, the railroads and ships that transport fuels, the wires that bring electricity to virtually every home. Nocera estimates the number at $150 trillion since the mid-19th century, and it is the $150 trillion gorilla in the energy debate.

“There’s nobody in a Harvard lab or at MIT who’s going to make a discovery—one discovery—that’s going to change an infrastructure that this country built over 150 years,” he says. “You’re at hundreds of trillions of dollars. So what is one person with a bunch of students in a lab going to do?”

That is why he believes the revolution in renewable energy will happen not in the developed world, with its entrenched infrastructure and its impatient venture capitalists, but in places like Africa and India, where there is no existing infrastructure to block the way. And don’t mistake Nocera’s interest in the poor for altruism; it’s pure practicality.

“People say, ‘Oh, it’s so nice that Nocera is doing something for the poor.’ It makes my blood curdle! I’m not helping the poor. I’m a jerk! The poor are helping me. They don’t have an infrastructure, so they’ll walk you to a renewable energy future.”

Given his unconventional past, this future makes perfect sense to Nocera. “I can start looking back over my life, and I can see how my immigrant family and being poor Italians and following the Grateful Dead—it all fits in some way,” he says, face brightening. “The whole energy project. I mean, and then you share it, and it’s distributed! The Grateful Dead!”

Harvard University and Wyss Institute: Bionic (Artificial) Leaf: Harvesting Solar Energy and Storing it as a Liquid Fuel


Harvad Bio Leaf_02_15_140-bionic-leafHarvesting sunlight is a trick plants mastered more than a billion years ago, using solar energy to feed themselves from the air and water around them in the process we know as photosynthesis.

Scientists have also figured out how to harness solar energy, using electricity from photovoltaic cells to yield hydrogen that can be later used in fuel cells. But hydrogen has failed to catch on as a practical fuel for cars or for power generation in a world designed around liquid fuels.

Now scientists from a team spanning Harvard University’s Faculty of Arts and Sciences, Harvard Medical School and the Wyss Institute for Biologically Inspired Engineering have created a system that uses bacteria to convert solar energy into a liquid fuel. Their work integrates an “artificial leaf,” which uses a catalyst to make sunlight split water into hydrogen and oxygen, with a bacterium engineered to convert carbon dioxide plus hydrogen into the liquid fuel isopropanol.

The findings are published Feb. 9 in PNAS. The co-first authors are Joseph Torella, a recent PhD graduate from the HMS Department of Systems Biology, and Christopher Gagliardi, a postdoctoral fellow in the Harvard Department of Chemistry and Chemical Biology.

Pamela Silver, the Elliott T. and Onie H. Adams Professor of Biochemistry and Systems Biology at HMS and an author of the paper, calls the system a bionic leaf, a nod to the artificial leaf invented by the paper’s senior author, Daniel Nocera, the Patterson Rockwood Professor of Energy at Harvard University.

Harvad Bio Leaf_02_15_140-bionic-leaf

“This is a proof of concept that you can have a way of harvesting solar energy and storing it in the form of a liquid fuel,” said Silver, who is a founding core faculty member of the Wyss. “Dan’s formidable discovery of the catalyst really set this off, and we had a mission of wanting to interface some kinds of organisms with the harvesting of solar energy. It was a perfect match.”

Get more HMS news here.

Silver and Nocera began collaborating two years ago, shortly after Nocera came to Harvard from MIT. They shared an interest in “personalized energy,” or the concept of making energy locally, as opposed to the current system, which in the example of oil means production is centralized and then sent to gas stations. Local energy would be attractive in the developing world.

“It’s not like we’re trying to make some super-convoluted system,” Silver said. “Instead, we are looking for simplicity and ease of use.”

In a similar vein, Nocera’s artificial leaf depends on catalysts made from materials that are inexpensive and readily accessible.

“The catalysts I made are extremely well adapted and compatible with the growth conditions you need for living organisms like a bacterium,” Nocera said.

In their new system, once the artificial leaf produces oxygen and hydrogen, the hydrogen is fed to a bacterium called Ralstonia eutropha. An enzyme takes the hydrogen back to protons and electrons, then combines them with carbon dioxide to replicate—making more cells.

Next, based on discoveries made earlier by Anthony Sinskey, professor of microbiology and of health sciences and technology at MIT, new pathways in the bacterium are metabolically engineered to make isopropanol.

“The advantage of interfacing the inorganic catalyst with biology is you have an unprecedented platform for chemical synthesis that you don’t have with inorganic catalysts alone,” said Brendan Colón, a graduate student in systems biology in the Silver lab and a co-author of the paper. “Solar-to-chemical production is the heart of this paper, and so far we’ve been using plants for that, but we are using the unprecedented ability of biology to make lots of compounds.”

The same principles could be employed to produce drugs such as vitamins in small amounts, Silver said.

The team’s immediate challenge is to increase the bionic leaf’s ability to translate solar energy to biomass by optimizing the catalyst and the bacteria. Their goal is 5 percent efficiency, compared to nature’s rate of 1 percent efficiency for photosynthesis to turn sunlight into biomass.

“We’re almost at a 1 percent efficiency rate of converting sunlight into isopropanol,” Nocera said. “There have been 2.6 billion years of evolution, and Pam and I working together a year and a half have already achieved the efficiency of photosynthesis.”

Source: Harvard Medical School

Toward a low-cost ‘artificial leaf’ that produces clean hydrogen fuel


Articicial Leaf III towardalowcoFor years, scientists have been pursuing “artificial leaf” technology, a green approach to making hydrogen fuel that copies plants’ ability to convert sunlight into a form of energy they can use. Now, one team reports progress toward a stand-alone system that lends itself to large-scale, low-cost production. They describe their nanowire mesh design in the journal ACS Nano.

Peidong Yang, Bin Liu and colleagues note that harnessing sunlight to split water and harvest hydrogen is one of the most intriguing ways to achieve clean energy. Automakers have started introducing cell vehicles, which only emit water when driven. But making hydrogen, which mostly comes from natural gas, requires electricity from conventional carbon dioxide-emitting power plants.

Articicial Leaf III towardalowco

Producing hydrogen at low cost from water using the from the sun would make this form of energy, which could also power homes and businesses, far more environmentally friendly. Building on a decade of work in this area, Yang’s team has taken one more step toward this goal.

The researchers took a page from the paper industry, using one of its processes to make a flat mesh out of light-absorbing semiconductor nanowires that, when immersed in water and exposed to sunlight, produces . The scientists say that the technique could allow their technology to be scaled up at low cost. Although boosting efficiency remains a challenge, their approach—unlike other artificial leaf systems—is free-standing and doesn’t require any additional wires or other external devices that would add to the environmental footprint.

Explore further: Harvesting hydrogen fuel from the Sun using Earth-abundant materials

More information: “All Inorganic Semiconductor Nanowire Mesh for Direct Solar Water Splitting” ACS Nano, 2014, 8 (11), pp 11739–11744. DOI: 10.1021/nn5051954

Abstract
The generation of chemical fuels via direct solar-to-fuel conversion from a fully integrated artificial photosynthetic system is an attractive approach for clean and sustainable energy, but so far there has yet to be a system that would have the acceptable efficiency, durability and can be manufactured at a reasonable cost. Here, we show that a semiconductor mesh made from all inorganic nanowires can achieve unassisted solar-driven, overall water-splitting without using any electron mediators. Free-standing nanowire mesh networks could be made in large scales using solution synthesis and vacuum filtration, making this approach attractive for low cost implementation.