Microkinetics-guided catalyst design for low-temperature CO catalytic oxidation

Abstract

Microkinetics was proposed to conduct crystal phase regulation for enhancing the low-temperature activity of SrCoO₃ perovskite towards CO catalytic oxidation. Experiments were then performed to validate the improved catalytic performance of the catalyst via phase regulation. The microkinetic results indicate that there is a linear scaling relationship between the adsorption energies of CO on the Co site and CO₂ on the oxygen vacancy. CO adsorption energy on the Co site and O₂ adsorption energy on the oxygen vacancy are identified as two reactivity descriptors, which can be used to establish volcano-type activity plots for screening highly efficient catalysts for CO catalytic oxidation. Co₃O₄ screened from volcano plots shows higher reactivity for CO catalytic oxidation than SrCoO₃. The crystalline phase of spinel-type Co₃O₄ is formed when the calcination temperature of SrCoO₃ synthesis decreases from 900 to 600 °C; the low-temperature catalytic activity is significantly enhanced and the temperature of CO complete conversion decreases from 400 °C to 250 °C. The in situ characterization results indicate that monodentate carbonate serves as an important intermediate of CO catalytic oxidation, which is governed by the Mars–van Krevelen (MvK) mechanism due to the lower energy barrier of CO oxidation by lattice oxygen. This work paves a new way to design highly efficient catalysts for CO catalytic oxidation.