A new “bionic leaf” system uses solar energy to produce liquid fuel. Credit: Courtesy of Jessica Polka/Silver Lab
New system surpasses efficiency of photosynthesis. Prof Nocera, and Prof Silver of Harvard University, have co-created a system that uses solar energy to split water molecules and hydrogen-eating bacteria to produce liquid fuels. “This is a true artificial photosynthesis system,” Nocera said. “Before, people were using artificial photosynthesis for water-splitting, but this is a true A-to-Z system, and we’ve gone well over the efficiency of photosynthesis in nature.”
While the study shows the system can be used to generate usable fuels, its potential doesn’t end there.”The beauty of biology is it’s the world’s greatest chemist – biology can do chemistry we can’t do easily,” she said. “In principle, we have a platform that can make any downstream carbon-based molecule. So this has the potential to be incredibly versatile.”
Dubbed “bionic leaf 2.0,” the new system builds on previous work which though it was capable of using solar energy to make isopropanol, faced challenges, especially the fact that the catalyst used to produce hydrogen, a nickel-molybdenum-zinc alloy also created reactive oxygen species, molecules that attacked and destroyed the bacteria’s DNA. To avoid that problem, they ran the system at high voltages, resulting in reduced efficiency.
“For this paper, we designed a new cobalt-phosphorus alloy catalyst, which we showed does not make reactive oxygen species,” Nocera said. “That allowed us to lower the voltage, and that led to a dramatic increase in efficiency.” The system can now convert solar energy to biomass with 10% efficiency, far above the 1% seen in the fastest growing plants.
Nocera and colleagues were also able to expand the portfolio of the system to include isobutanol and isopentanol. Researchers also used the system to create PHB, a bio-plastic precursor, a process first demonstrated by MIT professor Anthony Sinskey. The new catalyst also came with another advantage – its chemical design allows it to “self-heal” – meaning it wouldn’t leech material into solution. “This is the genius of Dan,” Silver said. “These catalysts are totally biologically compatible.”
The system is already effective enough to consider possible commercial applications but within a different model for technology translation. Working in conjunction with the First 100 Watts program at Harvard, which helped fund the research, Nocera hopes to continue developing the technology and its applications in nations like India with the help of their scientists.
“If you think about it, photosynthesis is amazing,” he said. “It takes sunlight, water and air-and then look at a tree. That’s exactly what we did, but we do it significantly better, because we turn all that energy into a fuel.” http://news.harvard.edu/gazette/story/2016/06/bionic-leaf-turns-sunlight-into-liquid-fuel/
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