Pulsed reactivity on LaCoO3-based perovskites: a comprehensive approach to elucidate the CO oxidation mechanism and the effect of dopants

Abstract

In this contribution we focus on three lanthanum cobaltate perovskites: undoped, Sr-doped, and Cu-doped to investigate the effect of doping on reactivity. The catalysts are prepared by a citric acid route and characterized by X-ray diffraction, temperature programmed desorption, energy dispersive X-ray analysis, and BET specific surface area measurement. A pulsed reactivity experiment has been set up in order to investigate the catalytic oxidation reaction of carbon monoxide (CO). Within a single experiment, this analysis allowed evaluation of the oxygen storage capacity (OSC) and derivation of kinetic parameters to compare the behavior of the different catalysts. Compared to the traditional steady-state experiments, a clear insight into the reaction mechanism is obtained, providing a deeper mechanistic view on the role of the perovskite oxide. An active role of the oxygen species of the catalysts has been demonstrated, with the temperature of 350 °C representing a threshold for the activation of bulk oxygen mobility. The effect of doping has been discussed in terms of enhancement of the reducibility of the perovskite oxides, resulting in lower activation energies for the catalytic oxidation of CO.