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.

"What did you just chew?" he asked the crowd. "The sun! The beef was just the energy of sunlight."

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.

Picture of Dan Nocera
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."

Every day on his drive in to the Mallinckrodt Chemistry Lab at Harvard, Nocera passes the house where his grandparents lived in Medford, Massachusetts, the town where he was born. His family emigrated from the Nocera area of Umbria (hence the surname). Raised Catholic and trained as an altar boy, he quickly chafed at the family pressure to assimilate. "As a little boy, if I spoke Italian, my grandmother would take her shoe off and hit me, yelling at me in Italian," he recalls. "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.

Picture of Dan Nocera with a fuel cell
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.

Picture of a formula written on a whiteboard
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.

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.

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."

Picture of science equipment
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!"

Lead photograph by Deanne Fitzmaurice, National Geographic