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Algal protein provides more efficient way to split water and produce hydrogen

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December 26, 2011

Hematite nanoparticle film (red) with functional phycocyanin network (green) attached

Hematite nanoparticle film (red) with functional phycocyanin network (green) attached

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Recently, scientists from the Swiss research institute EMPA, along with colleagues from the University of Basel and the Argonne National Laboratory in Illinois took a cue from photosynthesis and discovered that by coupling a light-harvesting plant protein with their specially designed electrode, they could substantially boost the efficiency of photo-electrochemical cells used to split water and produce hydrogen - a huge step forward in the search for clean, truly green power.

Until the discovery of deep sea life forms that thrive in lightless hyrothermal vents, photosynthesis was considered the engine that drives all life on Earth. For those of us not dwelling in the chilly depths, that's still pretty much true - plants use solar energy to combine carbon dioxide and water to build sugars for energy storage (food for us) and structure (wood for heat and shelter) - the ultimate in green. Somewhere in that cascade of reactions, water is quickly and efficiently split into hydrogen and oxygen - a property understandably of great interest to proponents of clean energy.

If you're not a plant, one way to break water into its components is through the process many of us learned about in high school science class - electrolysis, the energy for which can be cleanly supplied by photovoltaic cells or hydroelectric power. Another technique, the focus of the Swiss/US collaborators, uses photo-electrochemical cells (PEC), which employ light energy to directly cleave water electrochemically - a process that skips the step of converting the light to electricity first.

The material of choice for PEC electrodes (site of the actual water splitting) has centered on metal oxides because some are photocatalytic (activated by light). Recently, titanium dioxide was in the news after it was shown to disperse organic air and water pollutants when activated by UV light. Hematite, a form of iron oxide (otherwise known as rust) proved even more promising because it responds to visible wavelengths and is cheap and abundant.

While working on his doctoral thesis at EMPA, scientist Debajeet Bora hit upon the idea of cross-coupling molecules of a light-harvesting plant protein with nanoparticles of hematite.

"I was inspired by the natural photosynthetic machinery of cyanobacteria where phycocyanin acts as a major light-harvesting component. I wanted to make artificial photosynthesis using ceramics and proteins," Bora said. "The concept of hematite surface functionalization with proteins was completely novel in PEC research."

Structure of the plant protein phycocyanin (Image: Protein Database)

The phycocyanin molecule

It turns out phycocyanin, a protein found in blue-green algae (cyanobacteria), when bound to the electrode surface, doubled the amount of photocurrent compared to that generated by the hematite-only electrode. In an area of science where even small incremental increases in efficiency are considered noteworthy, this new plant-assisted boost to hydrogen generation is big news indeed and bodes well for the on-going quest to supply affordable earth-friendly energy for all of us.

About the Author
Randolph Jonsson A native San Franciscan, Randolph attended the U.S. Naval Academy at Annapolis, Maryland before finding his way to the film business. Eventually, he landed a job at George Lucas' Industrial Light + Magic, where he worked on many top-grossing films in both the camera and computer graphics departments. A proud member of MENSA, he's passionate about technology, optimal health, photography, marine biology, writing, world travel and the occasional, well-crafted gin and tonic!   All articles by Randolph Jonsson
6 Comments

In the burning process. Hydrogen bonds to oxygen. This doesn't inform about any energy returned into the hydrogen for reuse in clean, truly green power.

Robert DuBois
27th December, 2011 @ 08:36 am PST

Efficiency does not necessarily mean bulk. What are they going to do, have a bunch of petri dishes with cyanobacteria in them sitting on top of their electrolysis machine waiting for the proteins in the electrodes to burn up? They're going to have to replace these proteins likely every few seconds if they want to convert bulk amounts of water. And how long must it take to remove the proteins from the algae and place on the electrodes? Likely much longer than the few seconds they are good for. I do not see any practicality coming out of this whatsoever, unless they can find some magical process for the proteins to regenerate outside of the algae too. Good luck with that.

Ethan Brush
27th December, 2011 @ 02:53 pm PST

Ethan,

Before posting a scathing hypothesis, it helps to read the original article linked above. Among other things, it says:

"Somewhat surprisingly, the light harvesting protein complex does not get destroyed while in contact with a photocatalyst in an alkaline environment under strong illumination. Chemists would have predicted the complete denaturation of biomolecules under such corrosive and aggressive conditions."

Gadgeteer
27th December, 2011 @ 05:31 pm PST

You do realise, don't you, that water, the product of burning hydrogen is the most significant green house gas, don't you? It's s great development but please don't put misleading labels on it.

Gary Kerkin
28th December, 2011 @ 10:36 am PST

@Gary I'm not sure what you are trying to say. If you remove the hydrogen from water H2O, you get oxygen. In order to burn hydrogen, oxygen is added. What doesn't burn comes out of the exhaust as water.

Gene Jordan
28th December, 2011 @ 02:54 pm PST

Ok, so we now have a way of producing H2 twice as effectively. The question remains, how close are we to achieving commercially efficient H2 production? That fact would put the article in perspective.

voluntaryist
29th December, 2011 @ 02:29 pm PST
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