Having characterized the initial and final states of the CO dissociation on the 81 TM surfaces, we extensively searched the CO dissociation reaction Transition States (TSs). To this end, the Improved Dimer (ID) and Climbing-Image Nudged Elastic Band (CI-NEB) methods were used. When necessary, i.e. when forces acting on the atoms in the TS were not sufficiently close to zero -implying that the found point is not a true stationary point of the potential energy surface-a Quasi-Newton optimization was carried out until forces were found to be below 0.03 eV•Å -1 . All the TSs were characterized as saddle points by vibrational frequency analysis, this is, with a single imaginary frequency.