An FTIR study on the formation of NCO surface complexes over Rh/CeO2

Fourier transferred infrared spectroscopy combined with mass spectrometry was used to follow the NO + CO reaction and the formation of adsorbed species. It was shown that when the reaction between NO and CO set in two absorption bands appeared in the FTIR spectra of Rh/CeO2 at 2180 and 2210 cm−1, which were not observed following the adsorption of reactants and products. Adsorption of HNCO on pure CeO2 at 200 and 300 K yielded the same spectral features suggesting that these bands belong to adsorbed isocyanate, NCO, species bonded to the CeO2. These results suggest that the spillover process of NCO from the Rh onto support proceeds even in the case of CeO2 used as a solid oxidizer in the three-way catalyst. NCO attached to ceria reacts with H2O resulting in the release of NH3.