Looking for a way to preserve the metallic copper surface, Andiappan Marimuthu, Jianwen Zhang, and Suljo Linic of the University of Michigan demonstrated that exposing the catalyst to visible light can solve the problem (Science, DOI: 10.1126/science.1231631). Working with copper nanoparticles deposited on silica in a packed-bed reactor, they found that illuminating the catalyst with a broadband visible light source increases selectivity for propylene oxide from 20% to 50%, although current processes that use acid catalysts or more expensive gold catalysts may approach 90% selectivity. Marimuthu and colleagues believe the copper atoms still oxidize on the nanoparticle surfaces. But light-induced localized surface plasmon resonance of the metallic copper core causes electron transfer to Cu–O bonds, weakening them and promoting reduction back to metallic copper. The researchers suggest the approach could be used to tune the oxidation state of other nanoparticle catalysts with a plasmonic core, such as gold or silver.
by Jyllian Kemsley |
April 01, 2013