{"id":658488,"date":"2013-05-16T16:29:47","date_gmt":"2013-05-16T20:29:47","guid":{"rendered":"http:\/\/gigaom.com\/?p=646300"},"modified":"2013-05-16T16:29:47","modified_gmt":"2013-05-16T20:29:47","slug":"hydrogen-energy-the-chloroplast-way-solar-to-fuel-with-the-artificial-leaf","status":"publish","type":"post","link":"https:\/\/mereja.media\/index\/658488","title":{"rendered":"Hydrogen energy the chloroplast way: solar-to-fuel with the artificial leaf"},"content":{"rendered":"

With atmospheric carbon dioxide recently hitting a record 400 parts per million<\/a>, the discovery of alternative renewable energy sources has taken on added urgency. One effort is the so-called \u201cartificial leaf,\u201d a photosynthetic system that uses light energy to split water molecules and produce hydrogen. Researchers at Lawrence Berkeley National Lab have recently published details<\/a> of their new nanowire-based system that mimics the way plant chloroplasts transport charged particles.<\/p>\n

The artificial leaf\u2019s titanium dioxide and silicon nanowires are arranged in an array that actually resembles a microscopic forest of straight pines. The key to achieving good solar-to-fuel conversion efficiency is the integration of the components — the nanowire semiconductors that absorb light, an interfacial layer, and co-catalysts for the water splitting reaction — in a structure that resembles and functions like a chloroplast.<\/p>\n

Plants are so efficient at turning sunlight into sugars partly because of what is termed the \u201cZ-scheme\u201d: the daisy chain of molecules that deliver a charged electron from a chloroplast to molecular energy production in the cell. The artificial leaf uses the Z-scheme, too, but with the silicon nanowires responsible for the hydrogen generation and the titanium dioxide nanowires contributing to the formation of by-product oxygen. The use of two semiconductor materials allows for a large part of the sunlight spectrum to be harnessed (the silicon works off visible light and the titanium dioxide uses UV), while the forest-like array of nanowires increases the surface area for the solar-to-fuel reactions, which are helped along by embedded catalysts.<\/p>\n

The artificial leaf has a conversion efficiency of 0.12 percent, comparable to that of natural photosynthesis<\/a>. To be commercially viable, the efficiency number will have to get into the single digit percentages, and companies like MIT spin-off Sun Catalytix have already chosen to refocus their efforts away from artificial leaf tech<\/a>. Replacing the current-limiting titanium dioxide anode in the system is the Berkeley researchers\u2019 next target for improving conversion efficiency.<\/p>\n

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