Drawing inspiration from Mother Nature in designing an ‘artifical leaf’

Producing an artificial leaf capable of harnessing Mother Nature’s ability to produce energy from sunlight and water via photosynthesis has been a long-sought goal for researchers aspiring to provide an environmentally-friendly way to free to world of its dependence on coal, oil, and other carbon-producing fuel sources. Now a group of Chinese scientists has presented a design strategy based on the chemistry and biology of natural leaves that could lead to working prototypes of an artificial leaf that captures solar energy and uses it efficiently to change water into hydrogen fuel.

The structure of green leaves provides them with an extremely high light-harvesting efficiency. Within their architecture are structures responsible for focusing and guiding solar energy into the light-harvesting sections of the leaf, and other functions.

For this reason the scientists from State Key Lab of Matrix Composites at Shanghai Jiaotong University, Shanghai, China, decided to mimic that natural design in the development of a blueprint for artificial leaf-like structures. It led them to their recipe for the "Artificial Inorganic Leaf" (AIL), based on the natural leaf and titanium dioxide (TiO2) - a chemical already recognized as a photocatalyst for hydrogen production.

The scientists first infiltrated the leaves of Anemone vitifolia - a plant native to China - with titanium dioxide in a two-step process. Using advanced spectroscopic techniques, the scientists were then able to confirm that the structural features in the leaf favorable for light harvesting were replicated in the new TiO2 structure. They found the AIL to be eight times more active for hydrogen production than TiO2 that had not been "biotemplated" in that fashion. AILs also are more than three times as active as commercial photo-catalysts.

Next, the scientists embedded nanoparticles of platinum into the leaf surface. Platinum, along with the nitrogen found naturally in the leaf, helps increase the activity of the artificial leaves by an additional factor of ten.

"This concept may provide a new vista for the design of artificial photosynthetic systems based on biological paradigms and build a working prototype to exploit sustainable energy resources," doctors Tongxiang Fan, Di Zhang and Han Zhou reported.

Using sunlight to split water into its components, hydrogen and oxygen, is one of the most promising and sustainable tactics to escape current dependence on coal, oil, and other traditional fuels. That appeal is central to the much-discussed "Hydrogen Economy," and some auto companies, such as Honda, have already developed hydrogen-fueled cars. Lacking, however, is a cost-effective sustainable way to produce hydrogen. Drawing on Mother Nature could well provide the answer.

The team from the State Key Lab of Matrix Composites at Shanghai Jiaotong University will present its design strategy report at the 239th National Meeting of the American Chemical Society being held this week.