Influence of Precipitation Conditions on Properties of Ceria and their Implications on the Mars‐van‐Krevelen Active Surface Area

Abstract

AbstractQuantifying the active surface area of Mars‐van‐Krevelen catalysts is paramount for the elucidation of structure‐property relationships and the knowledge‐based catalyst development. Different cerium oxides were prepared via precipitation‐based techniques. By altering conditions during precipitation, materials with a wide span of material properties were prepared. The influence of temperature during ammonia‐based precipitation was investigated. When using Ce(IV) precursors an increase in precipitation temperature decreases the crystallite size while increasing specific surface area, attributed to an increase in nucleation rate. Sintering stability is also increased for materials precipitated at higher temperature. Measuring the total oxygen storage capacity (TOSC) values of the prepared materials showed that the TOSC is not strictly a function of BET surface area. Our results suggest that crystallites with a domain size under a certain threshold are not reduced via oxygen release but rather hydroxyl formation. A method was proposed with which the redox active surface area for polycrystalline ceria can be estimated on basis of the domain size obtained from Rietveld refinement. These findings were corroborated by CO oxidation light‐off experiments in which the light‐off temperature was found to correlate with the surface that can release oxygen reversibly, the Mars‐van‐Krevelen active surface area, rather than BET surface area.