AN IR STUDY OF CO-SENSING MECHANISM ON AU ZNO

An FTIR and quadrupole mass study of the adsorption and oxidation of C O on an Au/ZnO sample with O-16(2) and O-18(2) is presented. The resul ts indicate that CO adsorbed on gold sites at the perimeter interface with ZnO reacts with surface lattice oxygens at the oxide surface to f orm carbonate-like intermediates. This reaction and the decomposition of the intermediates can be assumed to be mainly responsible for the c onductivity changes of the semiconductive metal oxide caused by CO in air. Oxygen, present in the mixture and adsorbed on gold vicinal sites , makes the nucleophilic attack of surface oxygens on the CO easier as a consequence of an electron-withdrawing effect. This effect produces a positivization of the carbon of adsorbed CO by an inductive effect and activates the reactivity of support lattice oxygens on the CO.