Hydrogen evolution from water/alcohol mixtures: effective in situ generation of an active Au/TiO2 catalyst

Gold standard: Au/TiO(2) catalysts, easily prepared in situ from different Au precursors and TiO(2), generate hydrogen from water/alcohol mixtures. Different alcohols, and even glucose, can serve as sacrificial reductants. The best system produces hydrogen on a liter scale, and is stable for more than two days. Deuteration studies show that proton reduction is likely the rate-limiting step in this reaction.

Hydrogen storage in formic acid amine adducts

Formic acid, containing 4.4 wt% of hydrogen, is a non-toxic liquid at ambient temperature and therefore an ideal candidate as potential hydrogen storage material. Formic acid can be generated via catalytic hydrogenation of CO2 or bicarbonate in the presence of an amine with suitable ruthenium catalysts. In addition selective dehydrogenation of formic acid amine adducts can be carried out at ambient temperatures with either ruthenium phosphine catalyst systems as well as iron-based catalysts. In detail we obtained with the [RuCl2(benzene)]2/dppe catalyst system a remarkable TON of 260,000 at room temperature. Moreover applying Fe3(CO)12 together with tribenzylphosphine and 2,2':6',2"-terpyridine under visible light irradiation a TON of 1266 was obtained, which is the highest activity known to date for selective dehydrogenation of formic acid applying non-precious metal catalysts.

Hydrogen generation at ambient conditions: application in fuel cells

The efficient generation of hydrogen from formic acid/amine adducts at ambient temperature is demonstrated. The highest catalytic activity (TOF up to 3630 h(-1) after 20 min) was observed in the presence of in situ generated ruthenium phosphine catalysts. Compared to the previously known methods to generate hydrogen from liquid feedstocks, the systems presented here can be operated at room temperature without the need for any high-temperature reforming processes, and the hydrogen produced can then be directly used in fuel cells. A variety of Ru precursors and phosphine ligands were investigated for the decomposition of formic acid/amine adducts. These catalytic systems are particularly interesting for the generation of H2 for new applications in portable electric devices.