Oxygen Vacancy Promoted O₂ Activation over Perovskite Oxide for Low-Temperature CO Oxidation

Abstract

The insights on the primary active oxygen specie and its relation with oxygen vacancy is essential for the design of low-temperature oxidation catalysts. Herein, oxygen vacancy-rich La 0.8 Sr 0.2 CoO 3 with an ordered macroporous structure was integrated on the commercial ceramic monolith in large scale without additional adhesives via a facile in situ solution assembly. The constructed macropores not only contributed to the oxygen vacancy generation in catalyst preparation but also facilitated favorable mass transport during catalytic process. Combined with theoretical investigations and EPR, O 2 -TPD, H 2 -TPR observations, we revealed that monatomic oxygen ions (O − ) are the primary oxygen active specie for perovskite oxide. And molecular O 2 is more favorably adsorbed and activated on surface oxygen vacancies via a one electron transfer process to form monatomic oxygen ions (O − ), thus boosting richness of active O − and the low-temperature oxidation of CO. Different with the preferential Eley−Rideal (E-R) mechanism on pristine LSCO surface, Langmuir−Hinshelwood (L-H) mechanism, in which O − reacts with adsorbed CO to finish the oxidation reaction, was more favorable on the oxygen vacancy rich surface. Our work here elucidates the primary active oxygen specie as well as its origin over perovskite oxides and paves a feasible pathway for rational design of high-performance catalysts in heterogeneous reactions.

Catalytic performance of the Ce-doped LaCoO3 perovskite nanoparticles

“…An observed low-temperature peak in between 260 and 460 °C, whereas high-temperature peaks were observed between 475 and 650 °C temperature ranges. At lower temperature H 2 -consumption peak is attributed to the reduction of Co 3+ to Co 2+ and the reduction of the excess O 2 species and the chemisorbed oxygen on the surface of the catalysts, while reduction peak observed at high temperature (595 °C), is ascribed to the reduction of Co 2+ into metallic cobalt (Co 0 ), and the reduction of chemisorbed oxygen caused by lattice defects, as reported in literature 34,[51][52][53][54] . With the introduction of 5% Ce, the H 2 -consumption peaks progressively shifted towards lower temperature.…”

A Resol‐Assisted Cationic Coordinative Co‐assembly Approach to Mesoporous ABO3 Perovskite Oxides with Rich Oxygen Vacancy for Enhanced Hydrogenation of Furfural to Furfuryl Alcohol

“…The concentration of oxygen vacancy on O V ‐rich meso‐LMO reaches 1.32‐ and 3.34‐fold than that of meso‐LMO and bulk LMO, respectively, in good agreement with the O 1s XPS analysis. Furthermore, the ratio of adsorbed oxygen species/lattice oxygen species from O 2 ‐TPD spectra of O V ‐rich meso‐LMO, meso‐LMO, and bulk LMO are 1.20, 0.895, and 0.211, respectively, confirming that Ov‐rich meso‐LMO possess the larger proportion oxygen vacancies in all oxygen species [14] …”

“…[45] Obviously,O V -rich meso-LMO exhibits ab road and strong desorption feature in the range of 50-350 8 8C( peak at 98.1 8 8Ca nd peak at 287.6 8 8C), demonstrating high contents of oxygen vacancy species on O V -rich meso-LMO.The concentration of oxygen vacancy on O V -rich meso-LMO reaches 1.32-and 3.34-fold than that of meso-LMO and bulk LMO,respectively,ingood agreement with the O1sXPS analysis.F urthermore,t he ratio of adsorbed oxygen species/ lattice oxygen species from O 2 -TPD spectra of O V -rich meso-LMO,meso-LMO,and bulk LMO are 1.20, 0.895, and 0.211, respectively,confirming that Ov-rich meso-LMO possess the larger proportion oxygen vacancies in all oxygen species. [14] To get insights on the role of oxygen vacancies,D FT modeling is useful to disclose the atomic-level distinction of LMO perovskite oxide with different concentration of oxygen vacancy. [42,46,47] Accordingly to above data analyzation, three models were constructed for LMO:p erfect surface,t he surface with one oxygen vacancy and the surface with two oxygen vacancies on behalf of bulk LMO,m eso-LMO,a nd O V -rich meso-LMO,r espectively (Figure 3d-f).…”

“…[9][10][11][12] For instance,t he modified perovskite oxide La 0.8 Sr 0.2 CoO 3 with surface oxygen defects and surface Lewis acid sites was served as ac atalyst to effectively improve the activity of propane oxidation. [13] Furthermore,s ome research demonstrates that O 2 is more favorably adsorbed and activated on surface oxygen vacancies of La 0.8 Sr 0.2 MnO 3 , [14,15] which gives rise to the significantly enhanced activity for low-temperature CO oxidation. This provides inspirations for the adsorption and activation of oxygen-containing functional group of substrates on the catalyst surface with oxygen vacancies in the catalytic reaction and may lead to extraordinary catalytic activity.…”

Mn/Co Redox Cycle Promoted Catalytic Performance of Mesoporous SiO2‐Confined Highly Dispersed LaMnxCo1‐xO3 Perovskite Oxides in n‐Butylamine Combustion

“…[6] In general, A-site ions of perovskite-type oxides mainly played a role in stabilizing the structure, thus enhanced the stability of the catalysts during the catalytic process. [7] Meanwhile, the catalytic performances of perovskite-type oxides in VOCs combustion mainly relied on the redox nature of the B-site metal ions. Partial substitution of B-site ions of perovskite oxides could promote the redox couple of B-site ions and oxygen mobility, therefore improving their catalytic activities.…”