Ironing Out Hydrogen Storage

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Science  23 Sep 2011:
Vol. 333, Issue 6050, pp. 1714-1715
DOI: 10.1126/science.1211021

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The large-scale use of hydrogen (H2) as a clean transportation fuel—one of the great ambitions in the “hydrogen economy” (1)—must overcome several engineering issues. The flammability of H2 presents a safety hazard, and storing it under pressure, even with absorbent materials, adds unwanted weight to vehicles. One solution to this storage problem is to “carry” H2 in more stable chemical compounds that have a high hydrogen content. Ideally, these compounds are liquids at room temperature for easy delivery and release H2 with only a small release of heat to avoid energy losses. Small organic molecules such as alcohols (for example, methanol) or formic acid (HCOOH) fulfill these criteria. The release of H2 (and CO2 as a by-product) from HCOOH does not proceed spontaneously, and suitable catalysts are required for its dehydrogenation. On page 1733 of this issue, Boddien et al. (2) report a molecular iron complex that catalyzes H2 formation from HCOOH both at high rates and for many catalytic cycles.