Effect of Textural Structure on the Catalytic Performance of LaCoO₃ for CO Oxidation

Abstract

Bulk, supported, and porous perovskite LaCoO3 were prepared and their catalytic performances for CO oxidation were investigated. XRD, FTIR spectroscopy, SEM, TEM, and N2 physisorption measurements were performed to identify their structure, and temperature‐programmed desorption of oxygen, temperature‐programmed reduction by hydrogen, and X‐ray photoelectron spectroscopy were conducted to study their physicochemical properties. With the change from bulk to nanoparticles and further to a porous structure, the series of LaCoO3 samples showed increased oxygen vacancies and improved oxidizing ability, which led to enhanced catalytic performances for CO oxidation. The correlation of the CO oxidation activity with the amount of exposed metal sites indicated that the Co ions should be the active site of the reaction. Comparison of the activation energy supported the changes observed in the activities.

Aerobic selective oxidation of alcohols using La1−Ce CoO3 perovskite catalysts

“…Two reduction regions, located between 250 and 400°C and 450 and 650°C, are observed for all the samples (Fig. 3), which can be ascribed to the reduction of Co 3+ to Co 2+ and Co 2+ to Co 0 , respectively [24,33,34]. At lower temperatures, a main peak at 312°C and a shoulder at 352°C appear.…”

“…Those temperatures increase as the Ce content increases. According to the literature [24], the main peak can be assigned to the reduction of surface Co 3+ to Co 2+ and the removal of adsorbed oxygen species, while the shoulder peak is due to the reduction of bulk Co 3+ to Co 2+ , accompanied by formation of LaCoO 2.5 with a brownmillerite structure [35]. The temperature of the first reduction peak is almost the same for LaCoO 3 and La 0.95 Ce 0.05 CoO 3 , both have perovskite structures.…”

“…In view of the above, and given our past experience with perovskites [17,[21][22][23][24][25], we attempted to investigate if these oxides would also have the ability to activate molecular oxygen and subsequently catalyze the oxidation of organic substrates into desired fine chemicals at mild temperatures. Given the strong affinity of Ce 4+ to oxygen [22], La 1Àx Ce x CoO 3 (0 6 x 6 1.5) catalysts were prepared by a sol-gel method using methanol and ethylene glycol as complexing agents, with calcination at 600°C for 5 h. The LaCoO 3 activity and the efficiency for aerobic oxidation of alcohols at mild temperatures (e.g., 88°C) were compared with those of materials with cerium incorporated into the framework.…”

Comparison of the nickel addition patterns on the catalytic performances of LaCoO3 for low-temperature CO oxidation

“…However, they are easily deactivated due to the repair of oxygen vacancy by the molecular oxygen and possibly the transformation of surface morphology during the reaction. Perovskite oxides with ABO 3 structure are potential alternatives of noble metals and metal oxides in various applications including CO oxidation, due to their high thermal and structural stability, which enables a stable activity [7,8]. Indeed, many works reported that perovskite oxides are good catalysts for oxidation reactions, including the catalytic oxidation of toluene [9], nitric oxide [10], benzene [11], methane [12], and ethyl acetate [13].…”

Sol‐Gel Preparation of Perovskite Oxides Using Ethylene Glycol and Alcohol Mixture as Complexant and Its Catalytic Performances for CO Oxidation

“…The results are shown in Figure and Table . For Co 2p spectra, two peaks locating at 779.7 and 781.1 eV can be fitted, and are attributed respectively to Co 3+ and Co 2+ species ,. The peak locates at 789.9 eV is a satellite peak of the surface Co 2+ species .…”