Spinach power could provide electricity

A protein from spinach has been used in biohybrid solar cells. Image: JIANG HONGYAN/Shutterstock

Apparently Popeye the Sailorman isn’t the only one who can get a boost from spinach.

As far back as 1929, the cartoon character was using spinach for an energy boost that would power his “fisks”. Now five engineering students from Vanderbilt University in the US have shown us just how powerful spinach can be, by turning it into a biohybrid solar cell.

Over 40 years ago, scientists discovered that one of the proteins involved in photosynthesis, known as Photosystem 1 (PS1), could continue to function after it was extracted from various plants, including spinach. From this, they determined that PS1 converts sunlight into electricity with nearly 100 per cent efficiency — unlike manmade devices, which had efficiencies of less than 40 per cent.

Since this first discovery, scientists have been slowly and steadily developing ways to extract the protein and use it to produce long-lasting, electricity-making solar cells — not an easy task. “Nature knows how to do this extremely well. In evergreen trees, for example, PS1 lasts for years,” says associate professor David Cliffel, one of the team’s mentors. “We just have to figure out how to do it ourselves.”

His team developed a way to combine the PS1 from spinach with silicon, a material currently used in solar cells. They extracted the protein into an aqueous solution and poured the mixture on the surface of a p-doped silicon wafer, before evaporating the water to produce a one-micron-thick film of protein.

Their design, reported in the journal Advanced Materials, produced substantially more electricity than has been previously reported for biohybrid cells — nearly a milliamp (850 microamps) of current per square centimeter at 0.3 volts. That’s nearly two and half times than the best levels achieved by previous cells.

The next step is to create a functioning PS1-silicon solar cell using this design. And thanks to a US$90,000 grant from the EPA at the 8th Annual National Sustainable Design Expo, the team is on its way. “If we can continue on our current trajectory of increasing voltage and current levels, we could reach the range of mature solar conversion technologies in three years,” Cliffel says.

The five students also won the Marketplace Innovation Award from Paladin Capital and the Student Choice Award at the Expo for their innovation. “The team absolutely excelled in clearly presenting their engineering innovations to the public, says professor Kane Jennings, the team’s other mentor. “We were one of only two teams (out of 44) to win three awards.”

Source: Phys.org, Vanderbilt University

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