Copper Adds Splitting Water To Résumé

For the first time, chemists have prepared a homogeneous copper-based water-oxidation catalyst, opening a new direction in electrofuels research (Nat. Chem., DOI: 10.1038/nchem.1350). Sunlight-driven electrolytic water oxidation to make O₂ is a hot topic in catalysis because it is the more difficult half of the two-pronged reaction needed to split water to make H₂ for powering fuel cells. The best electrocatalysts to date are made from iridium and ruthenium. But chemists are interested in using less costly, Earth-abundant metals to meet anticipated future catalyst demand. For example, cobalt and iron are already being studied. Shoshanna M. Barnett, Karen I. Goldberg, and James M. Mayer of the University of Washington, Seattle, mixed copper salts and bipyridine at high pH, leading to in situ formation of the bipyridine hydroxo complex shown. Most soluble electrocatalysts require multistep preparation, they note. The researchers found that the catalyst promotes O₂ production at a rate of about 100 cycles per second, which is among the most rapid rates observed for soluble water-oxidation catalysts. The complex requires a moderate overpotential of 750 mV—the additional energy needed to push the reaction to completion—which Mayer says his team is trying to reduce.