5876–5881

A differential desorption technique, called intermittent temperature-programmed desorption (ITPD), was used to give new insights into the properties of La1 xSrxCo0.8Fe0.2O3 perovskites as a contribution to improve their performances with respect to various important application fields such as catalysis, electrocatalysis and solid oxide fuel cells (SOFC). Both ITPD and interrupted TPD (carried out at different heating rates) evidenced two distinct oxygen adsorbed states, desorbing at temperatures lower than 400 8C, corresponding to less than 5% of a compact monolayer of oxide ions. The first one, for low desorption temperatures (lower than 290 8C) exhibits a heat of adsorption (DH) distribution from 101 to 121 kJ mol 1. The second one, for higher desorption temperatures (between 290 and 400 8C) corresponds to DH = 146 4 kJ mol 1. Additionally, for temperatures higher than 400 8C, we observed a continuous desorption of oxygen species, probably originating from the subsurface or semi-bulk, with an associated activation energy of desorption 175 kJ mol 1.