Panasonic Corp announced July 30, 2012, that it has developed a system capable of artificial photosynthesis with as high an efficiency as plants.
In artificial photosynthesis, plant photosynthesis, which makes organic compounds from water, carbon dioxide and sunlight, is artificially realized.
This time, Panasonic achieved a solar energy conversion efficiency of 0.2%. Solar energy conversion efficiency is calculated by dividing the energy of formed materials by the energy of applied sunlight.
The efficiency of 0.2% is as high as the photosynthesis efficiency of plants that are used as biomass, the company said. Toyota Central R&D Labs Inc announced a similar system in September 2011, but its photosynthesis efficiency was 0.04%.
The newly-developed system uses nitride semiconductor electrodes and metal complex electrodes. At the nitride semiconductor electrodes, water is decomposed by using light energy, generating hydrogen ions (H+) and electrons (e-). And the electrodes for forming organic compounds mainly generate formic acid (HCOOH) by using carbon dioxide (CO2), two hydrogen ions (2H+) and two electrons (2e-).
Panasonic said that it solved the following two problems by using the nitride semiconductor. First, the energy state necessary for the reduction of carbon dioxide cannot be achieved without using multiple electrode materials. Second, in the case of existing complexes, even when the intensity of applied light is increased, the amount of reaction current does not follow it, making it impossible to fully utilize the intensity of sunlight.