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Andrea Frank
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Daniel Nocera
Henry Dreyfus Professor of Energy and Professor of Chemistry

What are you working on?

My field is solar energy conversion. We work to convert solar energy into chemical energy. Imagine a world where there is no need for oil. What will replace it? The answer is sunlight plus water. I could almost write an equation, sunlight + water = oil. It’s true that a lot of science has to happen before that is possible, but really, what is a fuel? What is oil? It’s a compound of high-energy bonds. When you burn the fuel, you get new
compounds, the bonds have less energy in them, and the energy that is released is the power that you use. So, when you burn oil or gasoline in a car, the chemical bonds of the gasoline rearrange with oxygen inside the piston to make CO 2 and water, and from this rearrangement you get energy.

Let me explain what I mean when I say sunlight + water = oil. In order to create energy from water, you must split the hydrogen and oxygen molecules. You’ve got to rearrange the bonds. Now, if you just shine sunlight on water nothing happens. So what’s my research? My research is to make the thing in between, the thing that catches the sunlight and then acts on the water to rearrange its low-energy bonds into high-energy bonds of hydrogen and oxygen. Oil already has the high-energy bonds, put there millions of years
ago by the compression of fossils and plant matter. It’s essentially stored solar energy. The bonds of water are low-energy. Therefore we must use sunlight to rearrange them into high-energy H 2 and O2 bonds. Once that is done, we can ––exactly as we do with oil––rearrange them again to create low-energy bonds of water, and the excess energy is what you use. Bond rearrangement is the essence of the energy problem. It is going to
be the science that delivers the gift of the sun as our power source.

How will you accomplish this?

We use nature as our blueprint. A leaf is a solar energy machine. It uses light to make oxygen and hydrogen. People don’t know that, but it’s a solid form of hydrogen (NADH) that gets stored with CO 2 to make sugar. So, we try to fi gure out how a leaf works. We do this by capturing its essential ingredients and making compounds that have its basic elements. Our task is to replace the leaf with a substance that can effectively do the same job. That’s called artifi cial photosynthesis. We literally build molecules that can capture light and then act on water to perform this hydrogen and oxygen splitting. After making the compounds bond by bond, we expose them to lasers in order to imitate the effects of the sun. The lasers allow us to turn the light on and off quickly and observe what happens to all that energy. The light produces an excited state. We can then take a series of pictures and follow molecules and energy fl ow. When we see how energy is captured in the excited state, we try to convey it to the water molecule. If we see that things aren’t working well we go back. It’s like being an engineer of molecules . We change the molecules around, we add things, we take things away, and, hopefully, we make a better molecule.

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Andrea Frank