FTIR study of the photo-induced reaction of NO plus CO on Rh/TiO2

The effect of UV illumination on the stability of Rh dicarbonyl on TiO2 and on the surface interaction of NO+CO gas mixture on TiO2 and Rh/TiO2 cataly sts was examined with FTIR spectroscopy. Photolysis of Rh-1(CO)(2) over TiO 2 caused the decomposition of this complex, and the formation of Rh-x-CO an d Rh-2(CO)(3) surface compounds. Illumination of the NO +CO/TiO2 system at 200 K produced a new band at 2212 cm(-1), which is attributed to the Ti-NCO species. This species is not observed in the absence of illumination even after extended adsorption time. Coadsorption of NO+CO gas mixture on Rh/TiO 2 gave an absorption band at 2160-2175 cm(-1), not detected after adsorptio n of NO and CO separately. This band is assigned to the vibration of NCO bo nded to the Rh. UV illumination dramatically enhanced the surface concentra tion of Rh-NCO surface species at both 200 and 300 K. It is assumed that th e extent of the electron transfer from TiO2 to the Rh is enhanced due to th e photoelectrons which leads to the greater probability of the surface diss ociation of NO, the key step in the formation of NCO surface complex.