Engineers at Indiana University (IU) have created an incredibly efficient biomaterial that speeds up the formation of hydrogen – the key component of fuel cells that use water to produce ignitable hydrogen and oxygen. Although these types of fuel cells aren’t new, this new modified catalyst, which combines the genetic material of a bacteria with a viral casing, produces hydrogen 150 times faster than the unaltered catalyst variant. The new research has been reported in the journal Nature Chemistry.
Hydrogen fuel cells come in two forms: photoelectrochemical (PEC) cells, which are driven by a form of artificial photosynthesis, and microbial fuel cells (MFCs), which use bacteria to catalyze a chemical reaction. In both cases, an electrical current is produced within the water source, which separates the positive hydrogen molecules from the negative oxygen-hydrogen ions. This process is known as electrolysis.
For this new study, researchers led by Trevor Douglas, the Earl Blough Professor of Chemistry in the IU Bloomington College of Arts and Sciences' Department of Chemistry, chose to speed up the hydrogen splitting part of the reaction using a novel catalyst-manufacturing technique.
Enzymes, particular protein structures that bind to specific chemical receptors, are biological catalysts. They can be artificially created by fusing certain types of material that are known to act as catalysts. A bacteria that is often used in MFCs is Escherichia coli (E. coli); it efficiently uses nutrients and converts them into carbon dioxide, free electrons and protons, the last two of which help produce an electrical current in the water.
With this in mind, the researchers extracted two genes from E. coli, hyaA and hyaB, both of which are vital components related to the production of the carbon dioxide, free electrons, and protons. These genes were then inserted into the protein casing of a virus, called a capsid, which protects them.
Normally, the capsid protects the genetic material of an actual virus, but in this case, these two bacterial genes are shielded by the casing of a virus known as bacteriophage P22. When assembled, this viral-like catalyst (“P22-Hyd”) acts as a powerful enzyme known as hydrogenase.
An artist’s rendering of P22-Hyd, the new catalyzing biomaterial that contains a hydrogen-generating enzyme within a viral shell. Credit: Indiana University
Remarkably, this enzyme is able to both break the chemical bonds of water in order to create hydrogen and work in reverse to recombine hydrogen and oxygen, imitating the ignition process that generates energy. “The reaction runs both ways – it can be used either as a hydrogen production catalyst or as a fuel cell catalyst,” Douglas said in a statement.
Combining the enzyme with a nickel-iron alloy, it was shown to easily integrate with other biomaterials typically found in various hydrogen fuel cells and to not suffer significant degradation in the presence of oxygen. Impressively, thanks to its protective viral shell, the catalyst was shown to not break down at room temperature, unlike its unaltered form.
When tested, the production of hydrogen using nickel-iron hydrogenase was shown to be 150 times higher than that of the unprotected, unaltered enzyme. This easily renewable, cheap to manufacture and environmentally friendly material, therefore, has a huge number of advantages over traditional fuel cell catalysts. “Incorporating this material into a solar-powered system is the next step,” Douglas added, referencing the PEC cells.