Ceramic microreactors show promise for portable electrical power sources, say US scientists.

For the first time, alumina microreactors containing porous silicon carbide 'monoliths' have been studied for on-site hydrogen production from readily available hydrocarbons.

Paul Kenis and colleagues at the University of Illinois at Urbana-Champaign have shown that the silicon carbide monoliths with a coating of ruthenium act as catalysts for high temperature 'steam reforming' reactions when integrated in high-density alumina housings. The monoliths are difficult to make, but, unlike typical oxide catalysts, their structure doesn't collapse at high temperatures - which is key to the catalysts' success, said Kenis.

'The microreactors can produce hydrogen from readily available hydrocarbon fuels such as propane without degradation of performance over time,' Kenis explained. 'To our knowledge, our microreactors produce the highest rate of hydrogen per volume compared to any work.'

Hydrogen fuel cells are highly efficient but there are safety issues related to distributing and storing compressed hydrogen. This makes on-site generation of hydrogen a preferred solution. The challenge, according to Kenis, has been finding ways to do this which avoid deactivating the catalyst by 'coking' - soot deposition. Kenis' microreactors can avoid this by operating at temperatures above 800 °C, which is achievable because of the silicon carbide materials used.

The next challenge for scientists is to integrate the microreactors into a complete fuel processing system, said Kenis.

Caroline Moore