CO2 is strongly adsorbed on Li/MgO as a surface carbonate and desorbs concomitantly with Li with an activation energy of desorption of 210 kJ/mol. The C2 product is strongly influenced by the presence of CO2, 0.5 Torr being sufficient to substantially lower the rate of C2 production and to establish an activation energy for reaction of 210 kJ/mol. In the absence of CO2, the activation energy of C2 production falls to 105 kJ/mol.