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September 28, 2009
Shining a light on green energy

By Carol Clark

Tianquan “Tim” Lian grew up in a fishing village, on a marshy coastline in southeast China’s Fujian Province. “It was hot, but beautiful, and there were lots of little creeks and inlets where you could fish at high tide and low tide,” says Lian, William Henry Emerson Professor of Chemistry.

Lian’s father worked in a government-owned department store. The family lived in a simple home that leaked during typhoons. “Food was not abundant,” Lian says, “and living conditions were worse than today, but we were happy. I would say very happy. It seemed to be a carefree time.”

Lian did well in school, enabling him to go to college, where he discovered the wonders of physical chemistry and quantum mechanics. Physical chemists explore the microscopic world through techniques such as spectroscopy — shooting lasers into an object to see how its atoms interact with light.

“I thought that was absolutely marvelous!” Lian says. “We can’t see molecules, but by shining a light on them and seeing what type of light they absorb and what type they release, you can deduce their structure and other properties.”

Today, Lian is a leading expert in ultra-fast spectroscopy, electron transfer processes and quantum dots — nano-particles that hold promise for everything from electronics to medicine and renewable energy.

In collaboration with scientists at Emory and elsewhere, Lian is studying ways to convert the sun’s energy into cheap and clean solutions to the global energy crisis. “Solar energy conversion is very complex,” he says. “Spectroscopy allows us to break it down into small, fundamental steps that you can study carefully.”

In a project with Emory inorganic chemist Craig Hill and computational chemist Jamal Musaev, Lian is investigating using sunlight to split water into oxygen and hydrogen, which could then be burned as a non-polluting fuel. “My lab has been looking at the charge separation process a long time, and the Hill and Musaev group is very good at making water oxidation catalysts — you need both in order to make solar-driven water-splitting work,” Lian explains.

They have demonstrated that they can shine a light on a stable, inorganic catalyst and split water into oxygen and protons. Protons can then be used to make hydrogen. “There are other groups that can split water using electricity, but we are one of the few who have shown that you can bypass electricity,” Lian says.

The most efficient catalyst for converting protons into hydrogen is a naturally occurring protein — hydrogenase. In another research project, Emory chemists are seeking ways to bind this protein to quantum dots, which are good at absorbing light and could provide the energy to drive the reaction. Lian is collaborating with Stefan Lutz, a biomolecular chemist who specializes in protein re-engineering, and Brian Dyer, a physical chemist who is an expert on hydrogenase.

Lian is also working on fundamental steps of converting solar energy into electricity. One promising area involves the relatively new technology of multiple exciton generation. The ability to generate multiple electrons from a single high-energy photon, and then separate them out of a quantum dot, holds the potential to greatly boost the current in a solar cell.

“These are all very challenging scientific problems,” Lian says, adding that it will take many people, working across disciplines, to make solar energy go mainstream. “We have to solve these problems, because using fossil fuels is not sustainable. We’re going to be in big trouble if all the developing countries start living the way we do in America.”

Lian visited his hometown in China over the summer. His parents now have air-conditioning in nearly every room of their home. “I was shocked,” he says. “When I was growing up, we had none.” And the Chinese government is touting plans to drive economic growth through the production of automobiles.

“I feel very good about what I do for a living,” Lian says. “It combines what I love, spectroscopy, with something that I feel very strongly about — the need to find sustainable, clean energy.”