New Design for an Artificial Leaf for More Efficient Hydrogen Production

Researchers at the State Key Lab of Matrix Composites at Shanghai Jiaotong University, Shanghai, China have described a new design strategy to produce an “Artificial Inorganic Leaf” (AIL), which could lead to working prototypes that capture solar energy and use it efficiently to change water into hydrogen fuel.

Part of the design on an artificial leaf. Credit: Tongxiang Fan. Click to enlarge.

Dr. Tongxiang Fan and colleagues presented their work at the 239^th National Meeting of the American Chemical Society (ACS) in San Francisco. It was among more than 12,000 scientific reports scheduled for presentation at the meeting, one of the largest scientific gatherings of 2010.

A natural leaf combines light harvesting, photo-induced charge separation and catalysis modules to capture solar energy and split water into oxygen and hydrogen. Fan et al. proposed a general strategy for the design and development of artificial inorganic leaves by assembling light-harvesting, photo conversion and catalytic modules (Pt/N-doped TiO₂ into an integrated functional unit with leaf-like hierarchical structures.

To create the AIL, 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.

The AIL is eight times more active for hydrogen production than TiO₂ that has 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.

In his ACS presentation, Fan reported on various aspects of Artificial Inorganic Leaf production, their spectroscopic work to better understand the macro- and microstructure of the photocatalysts, and their comparison to previously reported systems. The activity of these new “leaves”, are significantly higher than those prepared with classic routes. Fan attributes these results to the hierarchical structures derived from natural leaves.

Our results may represent an important first step towards the design of novel artificial solar energy transduction systems based on natural paradigms, particularly based on exploring and mimicking the structural design. Nature still has much to teach us, and human ingenuity can modify the principles of natural systems for enhanced utility.

—Dr. Tongxiang Fan

(A hat-tip to Jeremy!)

Resources

• Tongxiang Fan, Han Zhou, Di Zhang (2010) Artificial inorganic leafs inspired by natural photosynthesis (ACS 239)