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Researchers from MIT and Sun Catalytix develop an artificial leaf for solar water splitting to produce hydrogen and oxygen

(A) Plot of the efficiency vs. time for a wired configuration under AM 1.5 illumination. The traces are for solar cells of 7.7% PV efficiency. The cells were operated in a two-electrode cell configuration. (B) MS signal and SFE values for a wireless configuration. The cell was illuminated over the 2 h of the experiment. Reece et al. Click to enlarge.

Researchers led by MIT professor Daniel Nocera have produced an “artificial leaf”—a solar water-splitting cell producing hydrogen and oxygen that operates in near-neutral pH conditions, both with and without connecting wires. (Earlier post.)

In a paper published in the journal Science, they report that the cells carry out the solar-driven water splitting reaction at direct solar-to-fuels efficiencies of 2.5% (wireless configuration) and 4.7% (wired configuration) when driven by a solar cell of 6.2% and 7.7% light-to-electricity efficiency, respectively, and when illuminated with 1 sun of AM 1.5 simulated sunlight. The cells consist of a triple junction, amorphous silicon photovoltaic interfaced to hydrogen and oxygen evolving catalysts made from an alloy of earth-abundant metals and a cobalt-borate catalyst, respectively.

By constructing a simple, stand-alone device composed of silicon-based light absorbers and earth-abundant catalysts, the results described herein provide a first step down a path aligned with the low-cost systems engineering and manufacturing that is required for inexpensive direct solar-to-fuels systems.

—Reece et al.

Placed in a container of water and exposed to sunlight, the device quickly begins to generate oxygen from one side and hydrogen bubbles from the other. If placed in a container that has a barrier to separate the two sides, the two streams of bubbles can be collected and stored, and used later to deliver power: for example, by feeding them into a fuel cell that combines them once again into water while delivering an electric current.

Nocera, the Henry Dreyfus Professor of Energy and professor of chemistry at MIT, is the senior author of the paper, which was co-authored by his former student Steven Reece PhD ’07 (who now works at Sun Catalytix, a company started by Nocera to commercialize his solar-energy inventions), along with five other researchers from Sun Catalytix and MIT.

We show that water-splitting catalysts comprising earth- abundant materials can be integrated with amorphous silicon with minimal engineering to enable direct solar-to-fuels conversion based on water splitting. For the O2 evolving catalyst, we use a cobalt catalyst, Co-OEC, that self-assembles upon oxidation of Co2+, self-heals, and that can operate in buffered electrolyte with pure or natural water at room temperature. These attributes are similar to those of the OEC found in photosynthetic organisms.

The H2 evolving catalyst is a ternary alloy, NiMoZn. These catalysts have been interfaced directly with a commercial triple junction amorphous silicon (3jn-a-Si) solar cell (Xunlight Corp.) in wired and wireless configurations. For either, the cell uses stacked amorphous silicon and amorphous silicon-germanium alloy junctions deposited on a stainless steel substrate and coated with a 70 nm layer of Indium Tin Oxide (ITO). While the abundance of Ge may be a source of debate, the use of a silicon-based light absorber represents a major step towards a device composed of all earth-abundant materials for solar water splitting. Co-OEC is deposited directly onto the ITO layer (the illuminated side of the cell).

The NiMoZn alloy H2 catalyst was used in two configurations: (i) deposited on a Ni mesh substrate that is wired to the 3jn-a-Si solar cell and (ii) deposited directly on the opposing stainless steel surface of the 3jn-a-Si solar cell as a wireless device. The devices, which have not been optimized for performance may operate out of an open container of water containing borate electrolyte and with overall . The overall conversion efficiency of the wired cell indicates that a majority of the current from the solar cell can be converted directly to solar fuels and that a simply engineered functional artificial leaf comprising earth-abundant materials may be realized.

—Reece et al.

The new device is not yet ready for commercial production, since systems to collect, store and use the gases remain to be developed. Ultimately, Nocera sees a future in which individual homes could be equipped with solar-collection systems based on this principle: Panels on the roof could use sunlight to produce hydrogen and oxygen that would be stored in tanks, and then fed to a fuel cell whenever electricity is needed.

Such systems, Nocera hopes, could be made simple and inexpensive enough so that they could be widely adopted throughout the world, including many areas that do not presently have access to reliable sources of electricity.

Professor James Barber, a biochemist from Imperial College London who was not involved in this research, says Nocera’s 2008 finding of the cobalt-based catalyst was a “major discovery,” and these latest findings “are equally as important, since now the water-splitting reaction is powered entirely by visible light using tightly coupled systems comparable with that used in natural photosynthesis. This is a major achievement, which is one more step toward developing cheap and robust technology to harvest solar energy as chemical fuel.

There will be much work required to optimize the system, particularly in relation to the basic problem of efficiently using protons generated from the water-splitting reaction for hydrogen production. But there is no doubt that their achievement is a major breakthrough which will have a significant impact on the work of others dedicated to constructing light-driven catalytic systems to produce hydrogen and other solar fuels from water. This technology will advance side by side with new initiatives to improve and lower the cost of photovoltaics.

—James Barber

Nocera’s ongoing research with the artificial leaf is directed toward driving costs lower and looking at ways of improving the system’s efficiency.


  • Steven Y. Reece, Jonathan A. Hamel, Kimberly Sung, Thomas D. Jarvi, Arthur J. Esswein, Joep J. H. Pijpers, and Daniel G. Nocera (2011) Wireless Solar Water Splitting Using Silicon-Based Semiconductors and Earth-Abundant Catalysts. Science DOI: 10.1126/science.1209816



Regardless of one's view on a hydrogen economy, I think these boys deserve props for their work. Very impressive.


With the permanent loss of jobs in the U.S., diminished use of consumer credit, reduced driving miles, restaurant usage, and conspicuous consumption; i'm seeing a return to individual empowerment.

With the addition of personal energy generation, the world could see an individual autonomous structure for civilization that hasn't existed since the hunter/gatherers.

Such would be appropriate for an Earth Climate Change.


YAWN! BORING! We've seen these "artifical leaf" stories before....

Chad Snyder

ummm, that's how science progresses ejj.

unless you're a world renowned chemist, I'd say your comment is YAWN! BORING!

the artificial photosynthesis story sounded more like science fiction only a few years ago, but now it is really starting to appear viable.

better and cheaper batteries, better and cheaper fuel cells, better and cheaper solar panels -- the chemical convergences being developed right really are leading to game changing synergies.

hopefully we stay open-minded enough to realize the full potential of these technologies rather the believing we can predict the future of energy.

Yordan Georgiev

Vinod Khosla said it: If it can't scale, if it is not cheap enough , if it is not sustainable it will not survive ...


To cheaply split water for the hydrogen required to feed lower cost improved future FCs could mean the end of liquid fuels and ICE. If the converter is small and efficient enough, a (vehicle) roof top unit could one day produce all the hydrogen required, on sunny days. A larger residence roof top unit could do better. Storing hydrogen for rain days should not be a major problem.


Perhaps hydrate's could store H2 by day, release to FCs by night, yhihf


The whole thing is to capture and store solar energy.
We can do this with solar cells, but it is hard to store the energy. + we would like > 20% efficiency.

Grow plants for biomass.
react them with the H2 from these generators to create liquid HC fuels.
Much easier to manage than h2 storage, transmission and fuel cells.
Use them in HEV or small battery HEVs.


You'd need a big roof. At perhaps 70% efficiency for the fuel cell to convert the hydrogen back to electricity you are talking ball-park 2% overall efficiency.
So for a 1kw output you would need 50 square metres at 1kw per metre peak.
Of course, for average output day and night considering solar is only around 18% of nominal even in Phoenix and even more so to get power in winter you need more.
So if you have not got 500 square metres of roof or so, forget it.


Quote from the article" who now works at Sun Catalytix, a company started by Nocera to commercialize his solar-energy inventions ".

Im interrested to buy. Just sell this along with some more parts enouph to fill a tank of pure hydrogen at 5 000 psi. Then i will be ready to buy an hydrogen fuelcell car when they gonna hit the market so no need to have a public hydrogen infrastructure, just these gadjets in homes and small business.


Chad Snide er: The point is their findings are presented as if they are the first ones to ever create an artificial leaf, when in fact it has been done numerous times before. That is why it's boring.

william g irwin

Some of the reactions here are pretty harsh folks! Give these guys a break. Let them try to make commercial sense out of it as it develops. Sounds promising!
The main advantage I see of H2 is replenishment cycle.
However, in the short term, it seems to make more sense to compress CNG to 5000psi. Just what is the energy density comparison of H2 to CNG at pressuure? And remember that we already have an infrastructure for NG distribution in place. H2 makes more sense as a distributed source of local generators - like a gas station or local/regional fuel distribution system like we have for gasoline/oil now.

Ben Frigo-Vaz

Still not as efficient as simply hooking a solar cell to an electrolysis unit, or for that mater neither of those options are as efficient as hooking a solar cell up to a lithium ion battery, hence why hydrogen is a pipe dream that only diverts attention and money for options that are already more energy efficient and in more advance commercial development. The supposedly 20+ years when hydrogen is finally "ready" with volumetrically dense energy storage, cheap fuel cells and efficiency still by the laws of physics lower then many battery chemistries, batteries will have advanced so much as to make any advantage of hydrogen storage completely obsolete. Image metal air batteries using a metal particle paste that not flammable, not explosive, not under pressure or needing and wacky storage system unlike hydrogen. Cheap metals too like Zinc. With energy densities beyond 1000 wh/kg and the ability to mechanical refuel a metal air battery by simply pumping out oxidized paste and pumping in fresh paste and recycle the oxides externally, why bother with a highly volatile gaseous fuel like hydrogen? Long lasting Lithium Sulfur batteries will be commercial by 2020, Lithium-Air batteries have potential energy densities on par with diesel fuel, why focus on hydrogen???

Roger Pham

H2 is a synthetic chemical fuel that can be synthesized anywhere with a simple electrolytic device and electricity. Solar and wind energy harnessed in the summer, spring and fall could be stored in tanks and underground caverns, to be used in the winter for electricity and heating.

Zinc-air or Lithium-air batteries will be great, but the cheapness and simplicity of H2 generation (and storage) is still unrivaled. Fuel-cell vehicles will be commercially released by 2015 by most auto manufacturers.

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