Scientists have gotten a step closer to developing a bioinorganic hybrid approach to artificial photosynthesis.
The new system produces renewable molecular hydrogen and uses it to synthesize carbon dioxide into methane, which is a primary ingredient in natural gas, the Lawrence Berkeley National Laboratory reported.
"This study represents another key breakthrough in solar-to-chemical energy conversion efficiency and artificial photosynthesis," said Peidong Yang, a chemist with Berkeley Lab's Materials Sciences Division and one of the leaders of this study. "By generating renewable hydrogen and feeding it to microbes for the production of methane, we can now expect an electrical-to-chemical efficiency of better than 50 percent and a solar-to-chemical energy conversion efficiency of 10-percent if our system is coupled with state-of-art solar panel and electrolyzer."
To create hybrid artificial photosynthesis in a past model, the researchers used an array of silicon and titanium oxide nanowires that collected solar energy and delivered electrons to microbes, which reduced carbon dioxide into different value-added chemical products. In this new systes, the same array was used to harvest solar energy and split water molecules into molecular oxygen and hydrogen. This hydrogen was transported to microbes that reduced the hydrogen down to methane.
"In our latest work, we've demonstrated two key advances," said researcher Chris Chang. "First, our use of renewable hydrogen for carbon dioxide fixation opens up the possibility of using hydrogen that comes from any sustainable energy source, including wind, hydrothermal and nuclear. Second, having demonstrated one promising organism for using renewable hydrogen, we can now, through synthetic biology, expand to other organisms and other value-added chemical products."
In the previous system, the researchers used Sporomusa ovate, which is an anaerobic bacterium that uses electrons from their environment to reduce carbon dioxide. The new technique instead employs Methanosarcina barkeri, an anaerobic archaeon that reduces carbon dioxide using hydrogen instead of electrons. The new method is much more efficient than the previous technique, and has a much higher density for storing and transporting energy.
"While we were inspired by the process of natural photosynthesis and continue to learn from it, by adding nanotechnology to help improve the efficiency of natural systems we are showing that sometimes we can do even better than nature," Yang concluded.
The findings were published in a recent edition of the journal Proceedings of the National Academy of Sciences.
