11/15 - Seminar (inorganic): Morris Bullock, Pacific Northwest National Laboratory
Morris Bullock - speaker's webpage
Chemical and Materials Sciences
Pacific Northwest National Laboratory
Host: Paul Chirik
Design and Development of Molecular Electrocatalysts for the Production and Oxidation of Hydrogen: Shoving Protons Around With Proton Relays
Solar and wind power are carbon-neutral, sustainable energy sources, but their intermittent nature requires a reliable method of storing energy. Catalysts that efficiently interconvert between electrical energy and chemical bonds (fuels) are needed for a sustainable and flexible energy supply in the future. Reactions that involve transfer of multiple protons and electrons are pervasive in energy science, as exemplified by the two-proton, two-electron oxidation of H2 and the reverse, production of H2 by reduction of protons. Pendant amines incorporated into the second coordination sphere of metal complexes function as proton relays. The proton relays facilitate intramolecular proton mobility, as well as the movement of protons between the metal complex and acids or bases in solution.
Electrocatalysts based on inexpensive, earth-abundant metals ("Cheap Metals for Noble Tasks") are needed since low-temperature fuel cells generally use platinum, an expensive, precious metal. We are developing nickel(II) complexes with pendant amines that catalyze the oxidation of H2 at 1 atm. A related series of Ni(II) complexes have been studied in detail for electrocatalytic production of H2 by reduction of protons. Turnover frequencies as high as 100,000 s-1 were observed, though at a high overpotential. Iron complexes with pendant amines on the diphosphine ligand are also being studied, showing that it is possible to rationally design catalysts based on abundant, inexpensive metals as alternatives to precious metals. Organometallic Fe(II) complexes derived from CpFe(diphosphine)H, with pendant amines in the diphosphine ligands, mimic the reactivity of [FeFe]-hydrogenase enzymes, leading to heterolytic cleavage of the H-H bond.
Research carried out in the Center for Molecular Electrocatalysis, an Energy Frontier Research Center, is funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.