Moving Hydrides with Iron and Electrons through Metal Oxides: Biomimetic and Solar Fuels Approach to Hydrogen Utilization and Generation

The use and generation of hydrogen as a renewable fuel and feedstock is gaining importance as the pressure to diminish our dependence on fossil fuels grows. Nature has developed elegant methods to activate and utilize hydrogen, especially for the purpose of carbon dioxide CO2 fixation. One such enzyme, mono-[Fe] hydrogenase, uses a unique array of non-proteinaceous ligands to activate H2 and perform hydride transfer to the CO2-carrier substrate, H4MPT+. The iron center is ligated by a unique organometallic pyridone-acyl cofactor, which along with two carbonyls and a Cys-S stabilizes a low-spin Fe(II) center. We have developed a novel anthracene-scaffold ligand the mimics the biological coordination sphere – in both the identity and crucial facial geometry of the CNS donor set. Studies of H2 activation and hydride transfer will be discussed.

Second, a key component of solar energy storage is H2 generation from solar fuels devices. Our work utilizes a combination of silicon photoelectrodes, molecular interfaces and metal oxide passivating layers to achieve stable photoelectrochemical performance. The devices are characterized primarily by XPS and photoelectrochemistry. We have shown that the molecular nature of the interface between the electrode and the passivating metal oxide is critical in controlling electron transfer and, ultimately, the efficiency of H2 generation. We have utilized both molecular catalysts (PNP-Ni; Re-bpy) and Pt/Au nanoparticles for H2 generation and CO2 reduction. We are also investigating the use of embedded molecular wires in metal oxides (Al2O3, TiO2, ZnO) to enhance electron transport across these insulating oxide materials. Our newest findings will be highlighted.
Mike Rose (UT Austin)