Rust Boosts Artificial Photosynthesis, Research Finds — Brings Economical Artificial Photosynthesis One Step Closer

October 18th, 2013 by James Ayre

An important breakthrough has been made in the development of an economical means of harnessing artificial photosynthesis, according to researchers at Boston College — the voltage gap between the two core processes of oxidation and reduction has been reduced significantly via utilization of the common, and relatively cheap, material known as rust (iron oxide).

The researchers have apparently come within only “two-tenths of the photovoltage required to mimic oxidation and reduction, respectively, using unique photoanodes and photocathodes developed using novel nanowire components and coatings.” With this significant narrowing of the gap — while using only very economical materials — the day when artificial photosynthesis proves useful/practical for energy gathering/storing uses isn’t far off, according to the researchers.





“Many researchers have been trying to harvest solar energy and directly store it in chemical bonds,” stated lead author Dunwei Wang, an associate professor of chemistry at Boston College. “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.”

But “copying” highly complex natural reactions certainly isn’t always an easy thing to do, and in this case it “requires materials that can absorb sunlight broadly, transfer the energy to excited charges at high efficiencies and catalyze specific reduction and oxidation reactions,” as the researchers note — quite a list of demands.

The press release from Boston College explains:

Natural photosynthesis consists of two important processes. Oxidation produces oxygen gas. Reduction produces organic molecules. Artificial photosynthesis, also known as water splitting, tries 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. 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.

The researchers had already developed a new cathode preparation technique to improve hydrogen production — which means that there’s nothing really in the the way of a highly efficient photocathode being constructed. And now, with these recent advances in photoanode development, there’s not much left that needs to be overcome before (relatively) economical artificial photosynthesis is within reach.

The recent research, the Boston College note, “produced advances in photoanode development, where their engineered nanowire structures enabled the team to achieve a photovoltage of .6 volts using an iron oxide material. The voltage represents a 50% increase above the best prior results, which were reported last year. The team achieved the gains by coating hematite, an iron oxide similar to rust, with nickel iron oxide.”

“Already, the team has yielded more than 1 volt of power when combined with the photocathode they developed earlier this year,” Wang added. “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.”

A gap which now can be completely closed with only “minor” improvements.

The new research was just published in the journal Angewandte Chemie.









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