Decomposition of CO2 on (100)W

Abstract

Abstract The binding states and condensation kinetics of CO 2 and its decomposition products CO and O 2 on (100) W are examined by flash desorption mass spectrometry. Carbon dioxide desorbs almost entirely as CO and oxygen at all coverages. At saturation there are three major states of CO. These correspond to the high temperature states of CO alone although all peaks are shifted and amounts are altered slightly. Carbon monoxide exhibits four major binding states. All of these obey first order desorption kinetics as expected except the most tightly bound state which obeys second order kinetics. Desorption from a bimolecular complex is postulated to explain these results. Initial sticking coefficients of CO 2 , CO, and O 2 at 300°K are 0.85, 0.49, and 1.0 respectively. Coverage dependences indicate precursor intermediates for the states occupied at low coverages. The initial sticking coefficient of CO 2 varies rather slowly with substrate temperature, falling to 0.3 at 1200°K.