NO reduction with CO on metal nanoparticles/layered double hydroxides heterostructures obtained via the structural memory effect

Abstract

Nitrogen oxides are notorious air pollutants and the catalytic reduction of NOx by CO for removing NOx has attracted extensive attention. Herein, we present a series of ZnCu-layered double hydroxides (LDH) decorated with nanoparticles of metals (Me: In, Zn or Au) and the derived oxides as novel catalysts for NO reduction by CO. MeNP/ZnCu heterostructures were successfully prepared by taking advantage of the structural reconstruction of ZnCu LDH, via the structural memory effect, in the aqueous solutions of Me salts. X-ray diffraction (XRD), FTIR spectroscopy, H2-Temperature programmed reduction (H2-TPR), transmission electron microscopy TEM, X-ray photoelectron spectroscopy (XPS), and UV–vis spectroscopy have been used to characterize the structural, chemical composition, optical and nano/micromorphology of MeNP/ZnCu catalysts and the mixed oxides derived after the thermal treatment. Results indicate that on MeNP/ZnCu the reduction of NO by CO was 3 times higher than that of ZnCu while CO conversion was above 90%. Further, MeNP/ZnCu and the derived oxides demonstrated good stability in subsequent catalytic cycles while NO conversion was influenced by the molar ratio O2/CO. These findings indicate that the memory effect of the LDH can be effective as a simple strategy in the development of novel LDH-based heterostructured catalysts.