Direct solar-to-fuel ‘artificial leaf,’ the ‘Dead’ and the man behind the ‘personalized energy’ concept
It’s not often that the life and work of someone who labors in the fields of in materials science and chemistry is profiled in a magazine like The New Yorker—better know for its commentary, criticism and cartoons than for a thoughtful discussion of catalysts and silicon coatings—so it was a little startling to see a six-page story about Daniel Nocera and his “artificial leaf.”
Nocera is a someone I have been following since we began this blog four years ago because he seemed to be making some rapid advancements in understanding how to develop low-cost replacements for platinum as a catalyst in energy reactions. In particular, Nocera seemed extraordinarily confident that that he and his team at MIT would be able to use insights into photosynthesis to map a route to “artificial photosynthesis.” His goal has been simple, if not formidable: to mimic the ability of leaves to make chemical fuels from sunlight and water.
Actually, it seems like Nocera’s roadmap evolved into two parallel tracks. The first was to develop catalysts from earth-abundant materials that will facilitate the electrolysis of water into oxygen and hydrogen in a system wired to a fairly traditional photovoltaic energy technology; the second was to develop a method of applying the catalysts directly to silicon via a system of coatings that both perform the electrolysis and protect the silicon (via a metal oxide layer) in a water environment. In other words, the first part involves proving the ability of his electrolysis system wired to solar panels, and the second part involves eliminating the wires and sandwiching everything into thin units that just needs water and sunlight to work.
Nocera launched a company, Sun Catalytix, to execute the development. Along the way, a number of influential investors and institutions have stepped forward to back him and his company (including ARPA-E and Indian billionaire Ratan Tata) the work is starting to pay off in the form of working prototypes that can literally be dropped into water, including polluted water, and, when exposed to sunlight, immediately start producing bubbles of oxygen and hydrogen.
An extended description of high through-put construction of these artificial leaves is contained in a recent issue of Accounts of Chemical Research. In brief, the paper describes a leaf made “by interfacing a triple junction, amorphous silicon photovoltaic with hydrogen- and oxygen-evolving catalysts made from a ternary alloy (NiMoZn) and a cobalt–phosphate cluster (Co-oxygen evolving complex), respectively. … To stabilize silicon in water, its surface is coated with a conducting metal oxide onto which the Co-OEC may be deposited. The net result is that immersing a triple-junction Si wafer coated with NiMoZn and Co-OEC in water and holding it up to sunlight can effect direct solar energy conversion via water splitting.”
I always love to hear how people discover their love of science and engineering, and The New Yorker adds a lot of interesting color to Nocera’s life. The piece describes his early years as the son of a frequently transferred clothing buyer who learned the hard way that it was easier to invest in his interest in science (especially the legendary Heathkits) instead of temporary friendships. It goes on to describe him as evolving into a Deadhead, who both embraced the Grateful Dead’s music and the group’s philosophical leanings in favor of sharing and decentralization of their recordings (the band was notorious for freely permitting the recording and sharing of its concerts). “What I want to do with energy,” says Nocera, “is not different from what the Dead did with their music. I want to distribute it do everybody.”
More accurately, Nocera is mostly interested in getting energy to the impoverished world. In a recent interview, taped early this month at the Re3 conference, he talks about the artificial leaf technology as a “supercheap” low-tech, low-maintenance innovation that can bring “personalized energy”—gridless and decentralized—to the poorest regions of the world. He admits that by developed-nations’ standards, his systems would be considered minimal. But, he asserts, that the same systems could be transformational for people who have access to virtually no regular (let alone renewable) source of dependable power for illumination, cooking and communication.
Nocera emphasizes that the advantage of the artificial leaf isn’t comparative efficiency with traditional solar, but that particularly the hydrogen can be stored as a fuel, making it more versatile than battery storage.
Near the end of The New Yorker story, Nocera admits that his artificial leaves are, at best, decades away from being a practical solution, but he says the bottom line is stark. He says, “In the next forty years, three hundred and fifty million Indians are going to become energy users. We’ve got to get them energy, and it’s got to be CO2-neutral, because if they use coal we’re screwed.”
For more on Nocera, see our earlier posts: