Oct
16
Rust Gets Research Closer to Artificial Photosynthesis
October 16, 2013 | Leave a Comment
Chemists at Boston College have achieved a series of breakthroughs in their efforts to develop an economical means of harnessing energy using artificial photosynthesis with a nickel iron oxide component. By narrowing the voltage gap between the two crucial processes of oxidation and reduction the team reports it has come within two-tenths of a volt of the photovoltage required to mimic the oxidation and reduction processes.
Researchers at Boston College report that modifying the surface of hematite with a nickel iron oxide coating produces an increase in cathode photovoltage of nearly four-tenths of a volt. That’s nearly enough energy to put an economical method of artificial photosynthesis within reach. Click image for the largest view,
Using unique new photoanodes and photocathodes the team developed nanowire components and coatings. The team is narrowing cost gap using economical chemical components. The new developments take the research closer to using the human engineered reaction for unique applications such as solar energy harvesting and storage.
Lead author Dunwei Wang, an associate professor of chemistry at Boston College said, “Many researchers have been trying to harvest solar energy and directly store it in chemical bonds. Solar panels can harvest energy, but economical storage has remained elusive. We are trying to borrow a page from Mother Nature whereby photosynthesis produces energy from the sun and stores it.”
The challenge as Wang sees it, “Requires materials that can absorb sunlight broadly, transfer the energy to excited charges at high efficiencies and catalyze specific reduction and oxidation reactions.”
Plant’s way to convert sunlight to energy and material consists of two important photosynthesis processes. The oxidation produces oxygen gas, a waste material. Reduction produces organic molecules used for life.
Wang explains artificial photosynthesis, also known as water splitting, as trying to copy these two reactions using a photoanode to oxidize water and a photocathode to either reduce water for hydrogen production or to reduce carbon dioxide for organic molecules.
But in an artificial environment, a gap has persisted in the voltage required on either side of the reaction in order achieve these results, Wang said. In essence, oxidation and reduction require 1.2 to 1.3 volts combined to achieve the charge required to power artificial photosynthesis.
Previously, only rare materials allowed researchers bridge the gap, but those efforts are prohibitively expensive for widespread application. Wang and his lab have spent the past two years searching for inexpensive alternatives to bridge the voltage gap.
Earlier this year, the lab reported it had developed a new cathode preparation technique to improve hydrogen production. The findings removed most of the barriers to constructing an inexpensive, yet highly efficient photocathode, Wang said.
The team’s latest research produced advances in photoanode development, where their engineered nanowire structures enabled the team to achieve a photovoltage of 0.6 volts using an iron oxide material. The voltage represents a 50 percent increase above the best prior results, which were reported last year. The results put Wang and his team within two-tenths of a volt of the necessary photovoltage.
The team achieved the gains by coating hematite, an iron oxide similar to rust, with nickel iron oxide.
The team’s work has already yielded more than 1 volt of power when combined with the photocathode they developed earlier this year, said Wang. “Our system, made of oxygen, silicon and iron – three of the four most abundant elements on earth – can now provide more than 1 volt of power together. Now we are just two-tenths of a volt short on the photoanode. That’s a significant narrowing of the gap,” he said.
Wang knows closing the gap completely is entirely within reach, particularly since other researchers have used different systems to do so. He said his lab might partner with other researchers in an effort to close the gap. “With our innovations on the photocathode alone, this two-tenths of a volt is within reach. The real exciting part is that we were able to achieve six tenths of a volt using rust. That has never been done before,” he said.
Lets hope the partnering takes place. A privately owned low cost energy harvest and storage to useful fuel system is quite enticing.
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