Nanocrystals Make Hydrogen For Days

Researchers at the University of Rochester have developed a nanocrystal-based system that continuously generates hydrogen gas from light and protons for at least two weeks (Science, DOI: 10.1126/science.1227775). The catalytic scheme joins a growing list of strategies that strive to tear apart water molecules with sunlight to produce H₂, which can be used in fuel cells to produce electricity. In addition to using simple components such as Earth-abundant elements and visible light to make fuel, the researchers say their approach has the added benefit of being, to their knowledge, the longest-lasting nanoparticle-based photocatalytic system yet. To generate H₂, the researchers—including graduate students Zhiji Han and Fen Qiu and chemistry professors Richard Eisenberg, Patrick L. Holland, and Todd D. Krauss—irradiate an aqueous solution of nickel(II) nitrate, ascorbic acid, and di­hydrolipoic acid-coated CdSe nanocrystals with 520-nm light. The team thinks the light triggers electron transfer from the nanocrystals to a catalyst complex formed between nickel and dihydrolipoic acid. The catalyst complex then reduces protons supplied by ascorbic acid to form H₂. Aside from determining the structure of the nickel catalyst, the next step for the team, Krauss says, will be to improve the water-based system’s quantum yield, which is currently 36%.