Science and Technology

Fake leaves could make any home a power station

By Anne Eisenberg (New York Times)
Updated: 2011-06-26 07:38

Scientists are working on making artificial leaves that can produce fuels directly from sunlight, water and carbon dioxide, just as real leaves do. The new leaves could help people heat their homes and drive their cars.

"If nature can do it, so can we," said Gary Brudvig, a Yale University chemistry professor who studies photosynthesis, the process by which plants convert and store energy from the sun. "We want to use the principles from nature to design an artificial leaf," he said, adding that research groups around the world are working on the idea.

The artificial leaves will probably be thin sheets of plastic embedded with light-absorbing materials, or sheets of bubble-wrap-like material spread out over a field that take in sunlight and water vapor and emit, for example, hydrogen or methanol.

"Artificial leaves are inspired by leaves, but they won't look like them," said Nathan S. Lewis, a chemistry professor at the California Institute of Technology in Pasadena. He is the principal investigator for a five-year artificial-photosynthesis project that was awarded a grant of up to $122 million by the United States Department of Energy.

Artificial leaves are hardly new in laboratories, Dr. Brudvig said, but they have been too expensive, too fragile or too inefficient to compete commercially with fossil-fuel systems.

"We are going to take the best efforts from around the world," Dr. Lewis said, "and bring them together in a system to absorb sunlight at the right energy to make fuel."

Daniel Nocera, the Henry Dreyfus Professor of Energy at the Massachusetts Institute of Technology, wants to start by putting fake leaves on the roofs in developing countries.

"Our goal is to make each home its own power station," he said.

The leaf is made of inexpensive materials and works with ordinary water, he said.

In a demonstration, Dr. Nocera used a slim piece of silicon about the size of a playing card. The silicon was coated with catalysts, created by him and his group, that speed the breakdown of water into hydrogen and oxygen.

"On one side of the silicon, hydrogen starts bubbling up, and oxygen bubbles up on the other side," Dr. Nocera said.

The catalysts are placed directly on the silicon, so no extensive wiring is needed, as in standard photovoltaic cells, to convert sunlight into current and break down the water into hydrogen and oxygen. No extensive membrane is required, either. He plans to use the hydrogen as a fuel.

His system is designed for homes with modest energy needs. One of its advantages is that the water it splits into hydrogen and oxygen need not be pure.

Daniel R. Gamelin, a chemistry professor at the University of Washington in Seattle, said, "People in third-world countries may generate the hydrogen in the place they want to use it."

In 2008, Dr. Nocera formed a company, Sun Catalytix in Massachusetts, with financing from the Tata Group of India and Polaris Ventures Partners, among others. He said his partners at the company were working on commercial development of the technology.

Such systems could be transformative, Dr. Brudvig of Yale said.

"We don't have a system right now that can be used commercially for photosynthesis that competes with fossil fuels," he said. "But developing one is of central importance if we are to move from a fossil-fuel energy economy to a renewable-energy economy."

The New York Times

(China Daily 06/26/2011 page12)