Artificial photosynthesis - A tiny test for gardens of green energy

Artificial photosynthesis is the process of deriving energy from the sun by means similar to those used in plants. For two billion years, nature has used photosynthesis, and a similar process could open the way to new green energy technology.

Photosynthesis may hold the secret to efficient, cheap electrical production. But, typical efficiencies for solar cells typically hover around 15 percent. Despite this, solar power is the fastest-growing method of generating electricity. Therefore, the demand for more efficient solar cell designs is high. As new technologies are developed, they need to be tested, so researchers at Berkeley Labs have just built such a device.

They use two tiny sheets - a positively-charged cathode and a negatively-charged anode, separated apart from one another slightly by an ion-conducting membrane. The electrodes to be tested are inserted in the tiny device, and sunlight enters the system. This provides the energy to split water into its component molecules of hydrogen and oxygen. While the two gases are held apart from one another by the membrane, protons travel from the anode to the cathode, producing electricity. Any material may be used for anodes and cathodes in the device to test different designs, although the test bed is small.

"In our experimental realization of the design, a series of 19 parallel channels were fabricated in each device, with a total active area of eight square millimeters," Miguel Modestino, lead author of the research paper, said. Despite the small size of this test bed, the technology could be scaled up for larger-scale tests.

The device has already shown its ability to test mechanisms for splitting water molecules with sunlight. It can also be modified to test equipment designed for full artificial photosynthesis, as well as for conducting tests on fuel cells. Joel Ager was also among the team of material scientists at the Joint Center for Artificial Photosynthesis who developed this first-ever full-scale test bed.

"We've demonstrated a microfluidic electrolyzer for water splitting in which all functional components can be easily exchanged and tailored for optimization. This allows us to test on a small scale strategies that can be applied to large scale systems." Ager said.

Levels of carbon dioxide in the air recently reached 400 paprts per million (ppm) for the first time in human history. If all of the energy from sunlight that falls on Earth every hour could be harvested, it would power all human electrical needs for a year.

Research surrounding the development of the new testing equipment is profiled in the journal Physical Chemistry Chemical Physics.

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