Synthesis of LaxK1–xCoO3 nanorod and their catalytic performances for CO oxidation

Low temperature catalytic conversion of carbon monoxide by the application of novel perovskite catalysts

Automobile exhaust contributes the largest sources of carbon monoxide (CO) into the environment. To control this CO pollution, the catalytic converters have been discovered. The catalytic converters have been invented for regulating the CO discharge. There are many types of catalysts have been investigated for CO emission control purposes. Inorganic perovskite-type oxides are fascinating nanomaterials for wide applications in catalysis, fuel cells, and electrochemical sensing. Perovskites prepared in the nanoscale have recently received more attention due to their catalytic nature when used as electrode modifiers. Perovskite catalysts show great potential for CO oxidation catalyst in a catalytic converter for their low cost, high thermal stability and tailoring flexibility. It is active for CO oxidation at a lower temperature. The catalytic activity of these oxides is higher than that of many transition metals compounds and even some precious metal oxides. They represents attractive physical and chemical characteristics such as electronic conductivity, electrically active structure, the oxide ions mobility through the crystal lattice, variations on the content of the oxygen, thermal and chemical stability, and supermagnetic, photocatalytic, thermoelectric and dielectric properties. The surface sites and lattice oxygen species present in perovskite catalysts play an important role in chemical transformations. The partial replacement of cations A and B by different elements, which changes the atomic distance, causes unit cell disturbances, stabilizes various oxidation states or added cationic or anionic vacancies inside the lattice. The novel things disturb the solid reactivity by varying the reaction mechanism on the catalyst surface. Thus, the better cations replacement may represent more activity. There are lots of papers available to CO oxidation over perovskite catalysts but no review paper available in the literature that is represented to CO oxidation.

CO Oxidation Catalytic Effects of Intrinsic Surface Defects in Rhombohedral LaMnO3

There is an ongoing effort to replace rare and expensive noble-element catalysts with more abundant and less expensive transition metal oxides. With this goal in mind, the intrinsic defects of a rhombohedral perovskite-like structure of LaMnO₃ and their implications on CO catalytic properties were studied. Surface thermodynamic stability as a function of pressure (P) and temperature (T) were calculated to find the most stable surface under reaction conditions (P=0.2 atm, T=323 K to 673 K). Crystallographic planes (100), (111), (110), and (211) were evaluated and it was found that (110) with MnO₂ termination was the most stable under reaction conditions. Adsorption energies of O₂ and CO on (110) as well as the effect of intrinsic defects such as Mn and O vacancies were also calculated. It was found that O vacancies favor the interaction of CO on the surface, whereas Mn vacancies can favor the formation of carbonate species.