In the search for a clean, renewable energy source to replace fossil fuels, hydrogen has gained much attention as a possible fuel for the future. One of the challenges that must be overcome if this is to become a reality is an efficient way to produce and consume hydrogen. Currently, we have the technology to generate hydrogen from coal, natural gas, biomass and water. The majority of hydrogen currently produced comes from natural gas reformation, and hence does not help remove fossil fuel as an energy source. A variety of sustainable methods for hydrogen production are currently being researched, including solar, geothermal and catalytic hydrogen production.
Platinum is currently used to catalyze hydrogen production, but as Pt is expensive, found in limited supply, and easily poisoned by carbon monoxide during H production, it is not a practical for large-scale use. Catalysts inspired by the Fe–Ni active site of many hydrogen producing enzymes are particularly desirable due to the readily available and inexpensive metals.
The synthesis of Fe–Ni biomimetic catalytic complexes has proved difficult, primarily due to the extreme oxygen-sensitivity of such complexes. To date, only one example of a Fe–Ni model complex that is stable enough to withstand the range of electronic potential required for catalysis has been published.
When designing model complexes, it is crucial to preserve the key features of the active site of the Fe–Ni hydrogenases: the iron organometallic moiety with CO or CN ligands, nickel coordinated to terminal sulfur ligands, and the thiolate bridge between the metals. By preserving these traits of the enzyme active site, it is hoped that the synthetic complexes will operate at the electrochemical potential necessary for catalysis, have a high turnover frequency and be robust.