Catalytic combustion of methane conducted on La-B-O-C (B=Co, Mn, Fe) composites: The effects of B-sites cation properties

The novel La-B-O-C composites were fabricated as catalysts for methane catalytic combustion at low temperature, and considering the effect of newly C-O bond on B-site ions as active sites, three metal ions (Co, Mn, Fe) were selected for experiment. XRD, N-2-physisorption, XPS and H-2-TPR measurements were used to characterize the physicochemical properties of catalysts, which showed that the newly established C-O-B bond reduced the ionic valence of the B-site, and the redox capacities were increased or decreased to different degrees, respectively. Catalytic tests showed that T-50 of La-Co-C-O composites (LC-C) and La-Fe-C-O composites (LF-C) are 377 degrees C and 482 degrees C, much lower than that of unmodified catalyst, respectively. But T-50 of La-Mn-C-O composites (LM-C) increases to 507 degrees C from 493 degrees C. The superior performance of LC-C could be attributed to the high oxygen vacancies and enhanced redox property, and the better performance of LFC was mainly benefited from the increase in lattice oxygen. For LM-C, the sacrifice of Mn4+ weakened the catalytic activity. There are more obvious mechanistic differences for different B-site elements in the La-B-O-C. The study will bring innovative insights into the design of excellent composites catalysts for methane oxidation. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.