Enhancing carbon monoxide oxidation of Cobalt-Nickel containing a-deficient Perovskites through exsolution agents and reduction-oxidation pretreatment

In this work, different types of exsolution agents and pretreatment processes, comprising reduction-oxidation (RO) components, were introduced to modulate the exsolution process of A-deficient perovskites, La₀.7Ce₀.₁Co₀.₃Ni₀.₁Ti₀.6O₃. The catalysts were assessed using field emission scanning electron microscopy with energy dispersive spectroscopy (FESEM/EDS), X-ray Diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Their carbon monoxide (CO) oxidation activity was also compared. The results showed that the catalytic activity degraded at 520°C when hydrogen (E-H) was used as the exsolution agent. When RO components were introduced as exsolution agents (E-CO/O₂) or in the pretreatment (RO2% and RO18%), the deactivation at high temperatures was mitigated. The results of this study showed that RO18% was favourably pretreated with RO components, recording the highest CO conversion of 60.57% at 520°C and across all temperatures with no degradation at high temperature. It also recorded the lowest activation energy of 14.449 kJ/mol. The EDS, XRD, and XPS analyses of the catalyst demonstrated that the active sites for this reaction are primarily Co₂+ with Ni serving as the anchor between the metals and perovskites support. A high amount of lattice oxygen (O₂) with higher binding energy and chemisorbed O2 species also influenced the improved catalytic activity, attracting CO for reaction, reacting with the available surface O₂ and the faster replenishment of O₂ vacancies by the absorbed and bulk O2 lattice. These findings highlight the prospects of CO and O₂ inclusion in pretreatment for perovskite catalyst as options to reduce metal agglomeration and further improve CO oxidation activity.