MILAN - It could be an alternative and renewable solution to the use of fossil fuels. The news comes from researchers at Harvard University, who have developed a bionic leaf, that simulates photosynthesis and converts solar energy into liquid fuel. Daniel Nocera, professor and co-author of the research, explained: “Previously artificial photosynthesis was used to split water, but this is a complete system from A to Z: we went well beyond the efficiency of photosynthesis in nature”.
From the sun to water: the process
Photosynthesis is a biochemical process performed by plants containing chlorophyll which use the action of sunlight to transform water and carbon dioxide into organic compounds, essential for plant and animal life. The artificial leaf developed by researchers replicates this process since it uses solar energy to split the water molecules and the hydrogen-consuming bacteria in order to produce a liquid fuel. The major difference is in the results, given that this device for converting solar energy into biomass has an efficiency of 10%, well above the 1% obtained in nature with faster-growing plants.
The bionic leaf
The first device developed, while using solar energy to produce an alcohol (isopropanol), did in fact encounter numerous limitations in the catalyst used to trigger the reaction. In order to obtain hydrogen in the first stage of the process, the researchers resorted to a nickel, molybdenum and zinc alloy which demonstrated the disadvantage of producing reactive oxygen species, harmful to the bacteria to which the second stage was designated. To avoid this problem, the research group was then forced to operate the system at extremely high voltages, thereby greatly reducing the efficiency of the device.
While the researchers are confident in the fact that the efficiency of the bionic leaf can be increased further, the device seems ready to be tested in commercial applications, not to mention its importance in humanitarian work. According to Nocera, the bionic leaf is a significant discovery that demonstrates how better results can be obtained compared to photosynthesis itself. The goal now is to take the device to Developing countries, emerging from the usual technology transfer schemes.
by Alessandro Conte
November 21, 2016