Algal protein gives boost to electrochemical water splitting

December 19, 2011
Hematite nanoparticle film (red) with functional phycocyanin network (green) attached. Credit: Dr. E. Vitol, Argonne National Laboratory

Photosynthesis is considered the 'Holy Grail' in the field of sustainable energy generation because it directly converts solar energy into storable fuel using nothing but water and carbon dioxide (CO2). Scientists have long tried to mimic the underlying natural processes and to optimize them for energy device applications such as photo-electrochemical cells (PEC), which use sunlight to electrochemically split water – and thus directly generate hydrogen, cutting short the more conventional approach using photovoltaic cells for the electrolysis of water.

Traditionally, PEC electrodes are made of semiconducting materials such as metal oxides, some of which are also known for their photocatalytic properties. For quite some time, researchers at Empa's Laboratory for High Performance Ceramics (LHPC) have been investigating nanoparticles of these materials, for instance titanium dioxide (TiO2), for the neutralization of organic pollutants in air and water. Collaborating with colleagues at the University of Basel and at Argonne National Laboratory in the US, they now succeeded in making a nano-bio PEC electrode, consisting of iron oxide conjugated with a protein from blue-green algae (also known as cyanobacteria), which is twice as efficient in water splitting as iron oxide alone.

Inspired by photosynthesis

Iron oxide, in particular hematite (Fe2O3), is a promising electrode material for PEC because it is susceptible to visible wavelengths and thus uses sunlight more efficiently than photocatalysts like TiO2, which can only use the UV part of solar radiation. What's more, hematite is a low-cost and abundant material.

The second ingredient in the novel electrode 'recipe' is phycocyanin, a protein from blue-green algae. "I was inspired by the natural photosynthetic machinery of cyanobacteria where phycocyanin acts as a major light-harvesting component. I wanted to make artificial using ceramics and proteins», recalls Debajeet K. Bora who designed the new electrode during his PhD thesis at Empa. «The concept of hematite surface functionalization with proteins was completely novel in PEC research."

After Bora covalently cross-coupled phycocyanin to hematite nanoparticles that had been immobilized as a thin film, the conjugated hematite absorbed many more photons than without the algal protein. In fact, the induced photocurrent of the hybrid electrode was doubled compared to a 'normal' iron oxide electrode.

One tough cookie

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. "Photocatalysts are designed to destroy organic pollutants, which are a burden to the environment. But here we have a different situation", says Artur Braun, group leader at Empa's LHPC and principal investigator of the study. "There seems to be a delicate balance where organic molecules not only survive harsh photocatalytic conditions, but even convey an additional benefit to ceramic photocatalysts: They double the photocurrent. This is a big step forward".

Explore further: Unprecedented efficiency in producing hydrogen from water

Related Stories

Unprecedented efficiency in producing hydrogen from water

December 4, 2006

Scientists are reporting a major advance in technology for water photooxidation �using sunlight to produce clean-burning hydrogen fuel from ordinary water. Michael Gratzel and colleagues in Switzerland note that nature ...

Recommended for you

A new form of real gold, almost as light as air

November 25, 2015

Researchers at ETH Zurich have created a new type of foam made of real gold. It is the lightest form ever produced of the precious metal: a thousand times lighter than its conventional form and yet it is nearly impossible ...

Getting under the skin of a medieval mystery

November 23, 2015

A simple PVC eraser has helped an international team of scientists led by bioarchaeologists at the University of York to resolve the mystery surrounding the tissue-thin parchment used by medieval scribes to produce the first ...

Moonlighting molecules: Finding new uses for old enzymes

November 27, 2015

A collaboration between the University of Cambridge and MedImmune, the global biologics research and development arm of AstraZeneca, has led researchers to identify a potentially significant new application for a well-known ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.