Supplying the World's Energy Needs with Light and Water

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TR: And you've had some success putting what you've learned to use.

DN: We did make a compound that makes hydrogen using light. We have something that you can dissolve in solution, shine light on it, and hydrogen comes bubbling up. It didn't do it that efficiently. But it was a big advance because it had a lot of new concepts in there to show how you can use sunlight to make hydrogen.

TR: What are some of the research problems you're addressing that you hope can lead to a big step forward in solar?

DN: Something we've really been working hard at is [understanding] the design principles that photosynthesis operates off.

One is that when [photosynthesis] splits water into hydrogen and oxygen, it uses more than one electron. This current that's running is going one electron at a time. But then [the plant] stores them and uses four electrons at once. We don't know how to do multi-electron reactions very well. We don't even have theories to describe them.

And then you have to manage protons--and that's what biology does really well. It takes electrical current and then it converts it to a chemical current, and the thing conducting the chemical current is protons. And then it sends atoms. What a photovoltaic does is send electrons to a point. Photosynthesis actually sends not an electron but an atom. And that's even a tougher thing to do because atoms are so much heavier than electrons. So we've gotten down deep into understanding, how do you move atoms [such as hydrogen atoms] around from point A to B so that they can join up with each other? How do you assemble them so they can unite?

TR: You've written that chemistry "will likely play the most central role of all the sciences" in addressing energy problems. How would you summarize the role of chemistry?

DN: For game changers, it's really easy. There's three.

Make photovoltaics cheap, which is a lot of chemistry. It's inventing new materials to make PV cheap.

Replace noble metals--things like platinum--with abundant metals. Because there's not enough stuff. When you're talking about this much scale, you better be using things like iron and manganese. You better look at your book that says what are the most abundant elements on the face of the earth.

TR: And this is for fuel cells, and also for photovoltaics.

DN: Photovoltaics--everything. That's the real technology issue that you have to keep in your mind. Not something that's so great, it's 100 percent efficient--and oh, by the way, I'm using ruthenium. I can use ruthenium now to teach me a principle, but ruthenium's below iron [on the periodic table]. So I better figure out, how can I take everything I'm learning with ruthenium and apply it to iron?

TR: And the third game changer?

DN: Split water with light. You do those three things, and you have a full new energy economy. It's hard for me to say exactly what that technology will look like, because the science is missing. But at the beginning of the 1900s, we built an entire society based on a new energy system. And I believe, once solar is in place, with help from biofuel, with a little help from wind, we will invent our society again from a new energy source.