Researchers at Japan’s National Institute of Advanced Industrial Science and Technology (AIST) have found that found that Rhodium (Rh) nanoparticles (NPs) are highly active for catalytic decomposition of hydrous hydrazine to generate hydrogen and nitrogen under aqueous and ambient reaction conditions.
Their results, wrote the researchers in a paper published online in the ACS Journal of the American Chemical Society, offer a new prospect for an on-board hydrogen storage system. The team is currently working on improving the catalytic activity and selectivity.
Anhydrous hydrazine (N2H4), is a liquid at room temperature and has a hydrogen content as high as 12.5 wt%. However, in addition to being toxic, anhydrous hydrazine is also explosive when exposed to a metal catalyst. Hydrous hydrazine such as hydrazine monohydrate, while containing less hydrogen (7.9 wt%), is more stable.
...hydrous hydrazine might be a promising hydrogen carrier for storage and transportation that has the distinct advantages of easy recharging, the availability of the current infrastructure of liquid fuels for recharging, and the production of only nitrogen (which does not need recycling) in addition to hydrogen. In this context, the development of efficient and selective catalysts for H2 generation from hydrous hydrazine is of critical importance.—Singh et al.
The researchers examined the catalytic activities of Co, Ru, Ir, Cu, Ni, Fe, Pt, and Pd NPs under conditions analogous to those for the Rh NPs and found that the catalytic activity and selectivity strongly depend on the catalyst used, with Rh outperforming all the others.
They speculated that the observed enhancement in catalytic activity of the Rhodium might be due to the modification of metal particles during the synthetic process, which could presumably control the efficacy of the catalyst.
The fact that the catalytic activity and selectivity strongly depend on the catalyst used inspires us to search for more efficient and selective catalysts for this promising system.—Singh et al. (2009)
|Performance data from Acta hydrazine direct fuel cell. Source: Acta. Click to enlarge.|
Direct hydrazine fuel cell. Anglo-Italian catalyst maker Acta (earlier post), among others, has recently proposed using hydrazine directly in a fuel cell for automotive or portable applications. (Hydrazine fuel cells were developed much earlier for use in defense and aerospace applications.)
In 2007, Acta demonstrated performance with hydrazine fuel in alkaline membrane fuel cells up to 40% higher than previously reported best in class.
Alkaline exchange membrane fuel cells are similar to proton-exchange membrane (PEM) fuel cells, but the membranes transport hydroxide ions instead of protons.
Sanjay Kumar Singh, Xin-Bo Zhang, and Qiang Xu (2009) Room-Temperature Hydrogen Generation from Hydrous Hydrazine for Chemical Hydrogen Storage. J. Am. Chem. Soc. doi: 10.1021/ja903869y
Koji Yamadaa, Kazuaki Yasuda, Naoko Fujiwarab, Zyun Siromab, Hirohisa Tanakaa, Yoshinori Miyazakib and Tetsuhiko Kobayashib (2003) Potential application of anion-exchange membrane for hydrazine fuel cell electrolyte. Electrochemistry Communications Volume 5, Issue 10 Pages 892-896 doi: 10.1016/j.elecom.2003.08.015