NO reduction on Cu-ZSM-5 studied by EXAFS

Extended x-ray absorption fine structural (EXAFS) spectroscopy was used to study the nature of the Cu species in ZSM-5 involved in catalytic reduction of NO. The EXAFS data indicate that about 2.5 nearest oxygen atoms surrounding the center atom Cu with a Cu-O bond length of 1.95 Å in the oxidized Cu-ZSM-5 catalyst. Reduction of the catalyst in hydrogen at 573 K leads to the formation of Cu-Cu (2.53 Å) bonds. The coordination number (CN) of the Cu-Cu species in the reduced catalyst is 5.7. Over 90% of NO can be reduced to N₂ at 573 K effected by the Cu-ZSM-5 catalyst with the CN of the Cu-O bonding being 1.01.