Defect engineering technique for the fabrication of LaCoO3 perovskite catalyst via urea treatment for total oxidation of propane

Amorphization of LaCoO3 Perovskite Nanostructures for Efficient Oxygen Evolution

“…The increase in the size of LaCoO 3 −Reduce is attributed to the bonding effect with the assistance of urea during annealing process. 31 The corresponding EDS analysis (Figure S4) confirms the element content of LaCoO 3 perovskite before and after urea reduction, which shows that the amounts of La and Co for LaCoO 3 − Reduce and LaCoO 3 −Pristine are closed to 1:1. Taken together with the aforementioned results, it can be concluded that the amorphous LaCoO x catalyst is successfully synthesized via the annealing process of urea reduction.…”

“…In addition, scanning electron microscopy (SEM) images (Figure S3) show that LaCoO 3 –Reduce exhibits a rough surface structure compared with the nanoparticle structure of LaCoO 3 –Pristine. The increase in the size of LaCoO 3 –Reduce is attributed to the bonding effect with the assistance of urea during annealing process . The corresponding EDS analysis (Figure S4) confirms the element content of LaCoO 3 perovskite before and after urea reduction, which shows that the amounts of La and Co for LaCoO 3 –Reduce and LaCoO 3 –Pristine are closed to 1:1.…”

“…Here, the generated NH 4+ during pyrolysis of urea displaces La 3+ , weakly interacts toward CoO 6 octahedra, and forms N−H−O-Co configuration, and then the removal of N−H results in abundant defects to establish an amorphous structure for LaCoO 3 . 31 The enriched O2 in the LaCoO 3 −Reduce not only indicates the abundant oxygen vacancies are introduced into LaCoO 3 during urea reduction process but also provides great potential in accelerating the electrochemical OER, as these active oxygen species are one kind of electrophilic reagent and demonstrate high activity in catalytic oxidation. 36 The OER electrocatalytic activities of the LaCoO 3 −Reduce and LaCoO 3 −Pristine were evaluated by a three-electrode system in 1 M KOH solution.…”

“…For one thing, amorphization of LaCoO 3 perovskite nanostructures with the disordered structure and the regulated electronic properties provide high active-site density and large exposed surface area, which are available for electrocatalytic activities of the resulting LaCoO 3 toward water oxidation. 41,42 For another, the amorphous LaCoO x maintains a stable morphologic and electronic structure, which not only efficiently hinders the structure reconstruction that often existed in perovskite catalysts but also is the key to enhance OER durability. 42 In summary, we propose that the crystallized nanometer LaCoO 3 catalyst can be successfully transferred into an amorphous state through a simple urea reduction process.…”

“…Therefore, it is apparent that the oxygen vacancies content in LaCoO 3 –Reduce nanopowders is significantly larger than that of LaCoO 3 –Pristine, suggesting a certain amount of oxygen defects appears in the LaCoO 3 –Reduce nanopowders after urea reduction treatment. Here, the generated NH 4+ during pyrolysis of urea displaces La 3+ , weakly interacts toward CoO 6 octahedra, and forms N–H–O-Co configuration, and then the removal of N–H results in abundant defects to establish an amorphous structure for LaCoO 3 . The enriched O2 in the LaCoO 3 –Reduce not only indicates the abundant oxygen vacancies are introduced into LaCoO 3 during urea reduction process but also provides great potential in accelerating the electrochemical OER, as these active oxygen species are one kind of electrophilic reagent and demonstrate high activity in catalytic oxidation …”