Effect of thin [gamma]-Al.sub.2O.sub.3 coating modification containing Ce and P elements on the performance of Pd/[alpha]-Al.sub.2O.sub.3 foam-ceramic catalysts

• Published in: Journal of materials science 2023-05, Vol.58 (18), p.7528
• Main Authors: Wei, Yulin, Shi, Guopu, Ji, Jun, Liang, Fuxin, Ma, Deli, Li, Xinyu, Pang, Zhe
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Ceramic materials; Ceramics; Cerium; Palladium; Palladium catalysts; Phosphates
• ISSN: 0022-2461
• DOI: 10.1007/s10853-023-08427-1

It's crucial to make inexpensive, effective palladium catalysts employing [alpha]-alumina in the realms of pollution remediation and drug synthesis. The [alpha]-alumina foam ceramics prepared by the template approach were modified by adding a thin coating of [gamma]-alumina containing Ce and P elements to further prepare the palladium catalyst. [gamma]-Alumina significantly raised the foam's specific surface area, multiplied the number of acidic sites, decreased the Pd-O bond strength in palladium oxide, and brought the active phase content closer to the ideal value. Phosphate radicals were adsorbed onto the alumina surface, reducing the proportion of strongly acidic sites on the surface, and facilitating the desorption of oxygen species adsorbed by surface defects. As P and Ce elements interacted, the Ce.sup.4+/Ce.sup.3+ ratio decreased, increasing the number of oxygen vacancies in cerium oxide to improve the oxygen storage capacity of cerium oxide. In addition to acting as an oxygen storage material, the Ce elements increased the electron density of Pd and weakened the binding strength of the oxygen species bound to the individual metal Pd. There was a strong interaction between cerium and palladium, resulting in a mixed state of Pd.sup.0, PdO, and Pd.sup.2+ after the reaction. On the other hand, the surface of the foam was rough enough to facilitate the adhesion of the thin coating, while the thin coating, with a thickness of less than 8 [mu]m, improved its mechanical properties. The CO full conversion temperature was reduced by 135 °C in the Pd/CeP([gamma]/[alpha]-A) compared to the uncoated foam catalyst.