Merging [FeFe]-hydrogenases with materials and nanomaterials as biohybrid catalysts for solar H2 production

The catalysts commonly used for the H2 producing reaction in artificial solar systems are typically platinum or particulate platinum composites. Biological catalysts, the hydrogenases, exist in a wide-variety of microbes and are biosynthesized from abundant, non-precious metals. By virtue of a unique catalytic metallo-cluster that is composed of iron and sulfur, [FeFe]-hydrogenases are capable of catalyzing H2 production at turnover rates of millimoles-per-second. In addition, these biological catalysts possess some of the characteristics that are desired for cost-effective solar H2 production systems, high solubilities in aqueous solutions and low activation energies, but are sensitive to CO and O2. We are investigating ways to merge [FeFe]-hydrogenases with a variety of organic materials and nanomaterials for the fabrication of electrodes and biohybrids as catalysts for use in artificial solar H2 production systems. These efforts include designs that allow for the integration of [FeFe]-hydrogenase in dye-solar cells as models to measure solar conversion and H2 production efficiencies. In support of a more fundamental understanding of [FeFe]-hydrogenase for these and other applications the role of protein structure in catalysis is being investigated. Currently there is little known about the mechanism of how these and other enzymes couple multi-electron transfer to proton reduction. To further the mechanistic understanding of [FeFe]-hydrogenases, structural models for substrate transfer are being used to create enzyme variants for biochemical analysis. Here results are presented on investigations of proton-transfer pathways in [FeFe]-hydrogenase and their interaction with single-walled carbon nanotubes.