Berkeley lab researchers designing a bionic leaf

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In hopes of harnessing the energy from a bionic leaf of sorts, researchers at Lawrence Berkeley National Laboratory are developing technology that mimics photosynthesis to create and store solar energy.

At the Joint Center for Artificial Photosynthesis, scientists and graduate students from different universities are trying to design a new kind of solar cell powered by artificial photosynthesis. Such an approach would address the two key problems in solar energy: energy storage and the production of a potential carbon-neutral transport fuel.

In a study published last month in Physical Chemistry Chemical Physics, Gary Moore, principal investigator with Berkeley lab’s Physical Biosciences Division, along with a team of researchers, found that a certain hybrid material can do both.

“(The technology) allows you to generate a storable, transportable form of energy all-in-one device in an efficient way,” said T. Don Tilley, a campus chemistry professor and researcher at the Joint Center for Artificial Photosynthesis who was not part of the study.

The central problem with renewable energy is not simply generating it — the sun produces enough energy in one hour to power humankind for a year. The problem lies in storing power from an intermittent source, Moore said.

Currently, solar energy is stored in batteries, which is hugely inefficient. Instead, researchers want to convert sunlight into chemical energy by splitting water into oxygen and hydrogen and storing the hydrogen as a gas in the chemical bonds.

“Plants have had billions of years to do that; making sugar for them is no big deal — but we’re trying to do this inorganically,” said Kenneth Lee, a graduate student in mechanical engineering and research team member.

Hydrogen, which has more than 400 times the power density of a battery, has the kind of power essential to modern transport systems, Moore said, and is thus the best course of action for now. In the future, researchers can create hydrocarbons like methane, instead of just hydrogen gas, Lee explained.

In a process known as carbon dioxide reduction, solar energy can be used to convert carbon dioxide into higher-energy products. According to Tilley, plants do this already to make carbohydrates, but doing this artificially would require researchers to make something simpler than carbohydrates, such as methanol.

In the context of large-scale deployment, the Berkeley team wants to focus on systems that operate under “environmentally benign conditions using earth-abundant elements,” Moore said.

Moving forward, researchers will begin “material discovery,” looking for new metals and materials to split water and produce hydrogen fuel. Many of the most efficient semiconductors are also the most expensive, so researchers are trying to find a middle ground between efficiency and cost.

“Right now, we’re very early in the research stage, and what we are trying to do now is look for ways to drive down the cost,” Lee said.

Contact Bo Kovitz at [email protected] and follow her on Twitter @beau_etc.