Adjusting active sites and metal-support interactions of ceramic-loaded Pd/P-CeO2-Al2O3 coating to optimize CO2 methanation pathways

Abstract

Adjusting the active sites and metal-support interactions (MSI) of catalytic coatings on foam ceramics is a desirable strategy to improve CO2 methanation performance. By using a three-dipping and one-roasting technique, a highly active Pd/P-CeO2-Al2O3 catalyst (HA-Pd/PCA) with uniform three-dimensional mesh-like pores and daisy-like clusters was created. As PdO that was embedded in oxygen vacancies of CeO2 was reduced, oxygen vacancies were released. Pd then interacted with lattice oxygen close to the oxygen vacancies to create a strong MSI effect in the form of electron transfer. This translates to better Pd dispersion and more effective activation of the hydrogen. Moreover, the path of the hydrogen spillover that was necessary to hydrogenate the CO2 adsorbed in oxygen vacancies was shortened. In terms of the presence of acid-base sites, oxygen species, and oxygen vacancies, HA-Pd/PCA provided significant advantages. Based on this, the rate of carbonate to formate increased and the conversion pathway changed from a single bidentate formate to a dual pathway comprising bidentate formate and monodentate formate. The consumption and regeneration of hydroxyl groups were kept in balance. The outcomes demonstrated that HA-Pd/PCA had ideal stability, 100 % CH4 selectivity, and 86 % CO2 conversion.