News Story

July 24, 2012

Splitting Water to Save the Planet

Powering the Developing World's Poor with an 'Artificial Leaf'
By Alvin Powell

As the sun sets across rural Kenya, smoke rises from cooking fires in crooked gray columns that drift above the landscape. Smoke comes also from indoor fires, diffusing through the grass roofs of the traditional huts that dot the area. Women preparing supper make a thick cornmeal paste called ugali, to accompany leafy and nutritious kale, and perhaps some meat from a goat slaughtered that day at the nearby butcher’s shop.
   As the night deepens, families gather around the fire or talk around a table inside, their voices sounding against the musical backdrop of a battery-powered radio. The nearest electricity is miles away, at the small collection of shops and a gas station on the main road. Indoors, children do homework by the light from candles and kerosene lanterns.
   This scene of traditional rural life still plays out nightly in large parts of the developing world, where some 1.5 billion people live without electricity. As serene as the scene might seem viewed from the comfort of industrial world couches, the lack of power keeps poor people poor, robs them of good health, and denies them the advantages of an ongoing global revolution that provides ever greater information, ever easier communications, and ever richer entertainment for people in the electrified world.
   But the global, powerless poor aren’t forgotten. International development workers have long struggled—with both success and failure—to bring them modern health care, improved agricultural techniques, better education, and other benefits of industrialized society. The national and regional governments of impoverished nations also want to boost education, health care, and economic development, though they’re often hamstrung by some combination of inefficiency, inattention, lack of resources, and corruption. The United Nations (UN) sees access to electricity as a key step in achieving global health and development milestones and has therefore set a goal of universal access to power by 2030.
   Climate scientists, however, regard the global poor with more than a little worry. Though they don’t question their right to modernize, these scientists know that powering up another 1.5 billion people through conventional means will demand many more power plants, most likely fueled by oil, coal, and natural gas, the fossil fuels whose combustion is a major culprit in human-induced climate change. When expected population growth by mid-century is factored in, the number of new, conventional power plants needed daily to meet global demand is enough to boggle the mind, on the order of two 500 Megawatt facilities—each capable of powering 200,000 homes—between now and 2050.
   One scientist with an eye on the world’s energy poor is chemist Daniel Nocera, Dreyfus professor of energy at the Massachusetts Institute of Technology, who is moving up the Charles River next January to take a position at Harvard. Nocera shook up the scientific community in 2008 with the announcement of a process that allows scientists to easily mimic the power of plants to convert sunlight into energy through photosynthesis.
   Late last year, he created another stir, when in September he announced he had packaged his discovery with a small photovoltaic cell and created a device—the size of a pack of cards—that he called the first practical “artificial leaf.” When dropped into a glass of water and placed in the sun, the artificial leaf splits water molecules to generate oxygen and hydrogen gas, which when burned or combined in a fuel cell, can create enough energy daily to supply the modest power needs of a developing world home.
     Nocera has taken a keen interest in the global poor, those who live in what he calls the “non-legacy world,” places devoid of both power plants and the miles of lines and poles needed to move electricity from where it’s generated to where it’s needed. In his view, they are the world’s future. In coming decades, not only will the 1.5 billion people without power today be gaining it, but their communities will absorb a large portion of the additional two billion plus people expected as a result of global population growth by mid-century. Because of their sheer numbers, how those places go about developing and modernizing will determine not only their own future, but because of the climate implications of the fuels they use, will also influence environmental impacts throughout the world.
   “The people [who will be] driving the energy problem—it’s a whisper that’s going to become a cacophony—it’s going to be the poor and we need to take care of them,” Nocera says. “I never say I will help the poor. I always say the poor are going to help us because they’re going to teach us how to live in the future.”

A Tenacious Visionary

Nocera gained his most important training as a chemist in the 1970s during a time of fuel shortages and oil embargoes, while a doctoral student at the California Institute of Technology. It was then that he decided to work on photosynthesis, to understand and mimic what nature does in a leaf. He also recognized the long road ahead.
   “When I was a grad student, I realized I wanted to do energy and I wanted to do photosynthesis,” Nocera said during a recent interview in his MIT office. “[But] when I started looking at that, I realized whole pieces of science were missing.”
   Nocera knew that the key step, from an energy point of view, occurred relatively early in photosynthesis: the splitting of water into hydrogen and oxygen. That is when energy from the sun is captured and stored in chemical bonds. The plant, of course, is only halfway done at that point and goes on to combine the hydrogen and oxygen with carbon to create a carbohydrate, but to a scientist interested in photosynthesis not as a way to make little plants but rather as a way to catch the sun’s rays, once the water is split, the game is won.
   Splitting water is a complex process in photosynthesis. When a plant breaks a water molecule apart, the water isn’t broken directly into oxygen gas and hydrogen gas, mainly because the plant can’t handle hydrogen gas, Nocera says. Instead, oxygen is split from hydrogen and the hydrogen atoms are taken out in pieces, as protons and electrons.
   When Nocera began working on the problem in the early 1980s, he began by setting goals, not by the year, but by the decade.
   He first focused on understanding how to move the electrons. Eventually, Rudolph Marcus won the 1992 Nobel Prize in chemistry for mastering the trick with one electron. For his process to work, though, Nocera had to figure out how to do it with several.
   Once he had discovered a way, Nocera turned his attention to the proton. Working first in his lab at Michigan State University, where he taught for 13 years, and then at MIT beginning in 1997, he eventually realized that the proton and the electron had to be coupled to make it work. In other words, he couldn’t just take out the protons and then take out the electrons. It all had to be done at once, in what he describes as a choreographed dance now known by the tongue-twisting name of “proton-coupled electron transfer” (PCET).
   Nocera’s work proved fundamental in the new field of PCET, and became important in understanding how enzymes function. But he never lost sight of his long-term goal, understanding the key water-splitting step in photosynthesis.
   “While I was doing PCET, I was trying to figure out how electrons and protons couple for water splitting,” Nocera says.

A Self-healing Catalyst

In 2008, Nocera announced a process that mimicked the water-splitting reaction of a leaf. Its key elements were an electrode coated with a special catalyst made of cobalt and phosphate that created oxygen when a current was turned on, paired with a second electrode made of platinum that produced hydrogen. The most difficult piece—and the most elegant solution—was creating the oxygen-producing catalyst that accomplished the difficult first step in the water-splitting reaction.
   “The really hard part is the initial tearing of water apart,” Nocera says. “That’s what the leaf does, it makes oxygen first….Once you make O2 [from two water molecules], you have four protons and four electrons left over which, at your leisure, you can later use to make hydrogen.”
   Nocera’s cobalt-phosphate catalyst had a couple of benefits. First, it worked at room temperature in any kind of water, whether from the Charles River, a puddle outside the lab, or the ocean—an important trait if the process was to be useful in the developing world.
   Second, the catalyst was self-healing, meaning that though it gets broken apart in the reaction, as catalysts often do, it automatically re-assembles from its parts, making it ready for another round without having to be replenished.
   “That was totally different. Every other known material we used, we’d put it in water and watch it corrode,” Nocera says. “We made the first self-healing catalyst.”
   These traits gave Nocera’s process a leg up on a competing one developed in 1998 by John Turner at the U.S. National Renewable Energy Laboratory in Colorado. Turner’s system worked, but proved impractical for broader application because it used expensive chemicals that corroded rapidly.
   “The beauty of what we had done, what really kept getting us, was the simplicity,” Nocera says. “We had simple materials, they formed spontaneously from solution, you would just put a current in and they would self-assemble….”
   Nocera’s dream, however, was not just to create a chemical process. He wanted something he could drop in a glass of water, hold up to the sun, and watch work.
   After three more years of toil, he unveiled such a device in September 2011. He had created a photosynthetic sandwich, bonding the critical oxygen-splitting electrode to one side of a photovoltaic material, and a new, cheaper material to make hydrogen—an alloy of nickel, molybdenum and zinc—to the other side. Then he dropped it in water and held it up to the sun.
   Powered by the current from the photovoltaic, the two electrodes began producing bubbles of hydrogen and oxygen: fuel from the sun via an artificial leaf. The device is about 10 times more efficient at converting the sun’s rays to energy than a natural leaf and contains a breakthrough catalyst they know will operate for at least 45 days without a drop in activity.
   When placed in a gallon of water in the sun, the leaf generates a few hundred watts a day, enough to power a developing world home. Further, by coupling his artificial leaf with equipment to capture and store the oxygen and hydrogen gas, the device might solve the intermittency problem of solar energy: it could create electricity day and night. During the day the electricity from the solar cell would provide power to the home and run the water-splitting reaction. The gas would be stored for later use at night to power a fuel cell, which generates electricity and creates water as a byproduct.

Dreams and a Desperate Need

The group that might benefit most from Nocera’s device is actually much larger than the 1.5 billion people who are completely without access to electric power today. According to a 2010 report by the UN Advisory Group on Energy and Climate Change, another 1 billion are connected to unreliable power grids, and some 3 billion use biomass fuels for cooking, a practice that puts women and small children in smoke-filled kitchens daily, leading to an estimated 1.5 million excess deaths each year from lung disease caused by chronic smoke inhalation.
   To reach that disadvantaged population, the UN report calls for the global energy system to be “transformed” in the coming decades. If new, clean energy technology can be developed and distributed, it says, the global poor can leapfrog the industrialized world with systems providing sustainable, affordable energy. The report, which estimates the cost at $35 billion to $40 billion annually between now and 2030, suggests three strategies for effecting this transformation: extending the current grid; creating new, mini-grids powered by conventional or renewable sources; and creating distributed power sources for those entirely off grid. The last of these—distributed power systems—is of greatest interest to Nocera and others tired of waiting for governments and utility companies to extend existing power lines.
   “There’s a lot of interest in decentralized forms of energy,” says Henry Lee, senior lecturer in public policy at the Harvard Kennedy School and the
Jaidah Family director of the Environment and Natural Resources Program. “The argument here is we’ve been waiting decades for the existing urban system to electrify rural areas by
expanding transmission and distribution systems and…it hasn’t happened in a lot of places.”
   With a desperate need waiting to be filled, there is an opportunity for the right device coupled with the right business model, according to Lee and Tarun Khanna, the Lemann Professor at Harvard Business School and director of Harvard’s South Asia Initiative.
   “Demand is huge. There’s a small per capita demand, but the aggregate is massive,” Khanna says, “so it’s waiting for an entrepreneur to come up with a solution.” 
   In the developing world, parts of any major city will have reliable electricity, Khanna says, though typically those are areas where the wealthy and politically connected live. Other parts of the city will have intermittent power and families of means will have diesel generators that kick in when the grid fails. Large sections inhabited by the poor will have little or no power at all. Outside urban areas, electricity is rarer still.
   Even where there is power though, cost remains a hurdle. Electricity in rural areas is most commonly produced by diesel generators that, when the cost of the generator, fuel, and its transport over poor roads are considered, provide power at a cost of 20 to 30 cents per kilowatt hour.
   “Twenty-two cents, if it showed up on your bill [in the United States], you’d be having heart failure,” Lee says. “But if it’s in rural Cameroon, it’s not so bad.” 
   The high cost of power presents an opportunity for alternatives, Lee says. Renewables that are too expensive to catch on in developed nations, for example, may be able to gain a foothold in remote areas of the developing world, even though there will always be some families for whom almost any cost will be too high.
   When considering renewable alternatives, Lee has been most encouraged by solar power. Though photovoltaic panels are still too expensive to allow widespread adoption, their prices have been on a continual downward trend that, if it continues, will soon put them within reach of many more people.
   Lee and Khanna point to existing examples of breakthrough technologies. Cell phones are a “non-legacy” technology that has blossomed; with simpler infrastructure needs than traditional wired phones, they have spread all over the developing world as devices become cheaper.
   “From cellphones, you realize that a steep increase in efficiency makes a first order difference to adoption rates,” Khanna says. “The cost of mobile telephony has fallen so dramatically that it really is in every nook and crevice of the world. It has become an agent of change and this [artificial leaf] could be the same way.”
   Cellphone towers, powered by generators burning expensive diesel fuel, may also provide an opportunity in the developing world for photovoltaics, Lee said, if they can generate power more cheaply than diesel.
   Khanna offers three questions he says are important to consider for a new energy product such as Nocera’s. First, how much government support would the technology need at the beginning? Less is better, of course, and none better still, but some new technologies have benefitted from a government-subsidized boost. Second, how scalable is the technology? Can it grow from small pilot projects to widespread adoption? Third, how compatible would it be with the existing grid?
   A further critical factor in the successful adoption of a new technology like the artificial leaf is entrepreneurs who will not only sell devices, but also provide supplies and repair services.
   “I can get a grant from the World Bank or someplace to install a solar [photovoltaic] system. The guy who installs it comes from 300 miles away. He puts it up and leaves, then four weeks later it breaks down, the local people can’t fix it, and it never works again,” Lee points out. “For this [Nocera’s artificial leaf] to work, it’s not just getting the system [installed], it’s building the entrepreneurial system that maintains them. So you have to build entrepreneurs in those areas who specialize in low-margin renewable energy options because there aren’t a lot of margins to incur in poor villages.” 
   Lee suggests a model where power generation is anchored by other facilities. A rice-husking plant, for example, could anchor power generation fueled by burning rice husks, or by using the husks to make biogas and burning that to generate power. The husking facility might buy half the power generated to run its operations while the rest is distributed to the community.   
   “The key is to have the entrepreneur who can maintain the facilities and be the purveyor of [the devices],” Lee says.
   Ricardo Hausmann, director of Harvard’s Center for International Development and professor of the practice of international development, cautions against thinking that the developing world is rife with “entrepreneurs” waiting for opportunity. There’s a difference, he says, between passionate entrepreneurs like the founders of tech startups who create companies that employ thousands and people in the developing world who run a shop that employs three people and are essentially “entrepreneurial” because they have no other choice.
   Even with that caution, though, Hausmann welcomes innovations that might bring more electricity to the developing world. Electricity is a need so basic, he says, that many things flow from it. The Internet, whose information can be an equalizer between rich and poor, is obviously inaccessible without electricity.

Relief for a Global Climate

In September 2011, the same month that Nocera unveiled his leaf, the U.S. Energy Information Administration released projections that confirmed climate scientists’ fears about the future. The report projects that world energy use will grow 53 percent by 2035, with the fast-modernizing nations of China and India accounting for half the increase. Though renewable energy is projected to grow faster, fossil fuels will still account for 78 percent of world energy use in 2035, the report says. Carbon dioxide emissions are expected to rise 43 percent over the period, with most of the increase coming as the developing world catches up to consumption levels in industrialized nations.
   In the view of Harvard atmospheric chemist James Anderson, the climate situation is at crisis levels already. Many scientists believed that climate change’s effects would reach the point of no return when atmospheric carbon dioxide levels reached 350 parts per million. The world is approaching 400 parts per million today.
   “If there isn’t a clear pathway…to wean us off carbon-based fuel as a human community, we basically will march inexorably into tens of meters of sea level rise, the loss of all the glacial structures, first in the northern hemisphere, which removes the water supply for China, India, the western part of the U.S., and so on,”
Anderson says.
   Anderson, the Weld professor of atmospheric chemistry, believes Nocera’s work shows an enormous amount of promise. It addresses head on the problem of switching from high-carbon to low-carbon fuel sources, and also provides developing world societies with a way to transform themselves by freeing women from hours spent each day collecting wood and water.
   “We have a pathway into the future that is innovative, creative, responsible, and sustainable. If we follow the [existing] carbon fuel pathway even for the next few years, we’ve entered an irreversible stage that does nobody any good except for the vested interests that sell the stuff,” Anderson says. “This technique that Dan has developed allows the use of electrons and photons to take up a major part of the increase in per capita energy demand over the next 50 years.”

Building on Success

Nocera’s appointment as Rockwood professor of energy in Harvard’s department of chemistry and chemical biology generated a lot of excitement when officially announced in March. Eric Jacobsen, Emery professor of chemistry and chair of Harvard’s department of chemistry and chemical biology, says Nocera’s hire, effective January 2013, will fill several needs in a department whose most prominent inorganic chemist, Dick Holm, retired three years ago.
   “Inorganic chemistry is one of the canonical subfields of chemistry that really has to be represented in a strong department,” Jacobsen says. “Students were having to take courses at MIT just to fulfill requirements. It was really an acute need.”
   In addition to filling the department’s need for a top inorganic chemist on its faculty, Jacobsen says Nocera’s hire allows the department to join a greater conversation already ongoing across Harvard on one of the most important issues of our time: energy.
   “There’s quite a bit of effort at Harvard in areas related to energy, especially on the policy side—at the Kennedy School, the Business School, the Law School—but relatively little on the FAS [Faculty of Arts and Sciences] side,” Jacobsen says. “We know this is an area where we wanted to gain strength. It’s an important area, and obviously an area that will continue to be important in the future.”
   Nocera already has some agenda items to work on at Harvard. While promising, his leaf has a long way to go before it can be incorporated into a marketable product. Some development will proceed at the Cambridge-based startup, Sun Catalytix, that he established to help translate his discoveries into products. But more basic science research is also needed.
   One of the knottiest issues posed by Nocera’s photosynthetic approach to localized energy production is that it requires consumers to handle hydrogen and oxygen gas. Nocera acknowledges that difficulty and says it may be best to continue to crib from nature and convert the gases to a solid fuel like a plant’s carbohydrate, more easily handled in a low-resource setting. That’s something Nocera is looking forward to working on with Harvard’s community of organic chemists.
   Moving to Harvard gives Nocera greater access to experts in policy, business and even sociology, as well, all areas that may prove valuable as the artificial leaf moves from prototype to product. Harvard’s vast network of alumni, who work around the world in international development, public health, and leadership positions in government, will also help, he says.
   Nocera’s view of the future isn’t focused solely on the developing world, however. Closer to home, he’d like to see the Boston and Cambridge area become a global powerhouse in energy research and development, mirroring what it is already in medicine, the life sciences and biotechnology. The brains are already here at both Harvard and MIT, he says, and the right project and vision can pull in the necessary resources. “What’s happened here in biotech [can] happen here in energy. This will become energy central.”


This article has been adapted from Environment@Harvard, Volume 4 Issue 1.

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