New insights into the support morphology-dependent ammonia synthesis activity of Ru/CeO2 catalysts

Three ceria nanocrystals with different morphologies (nanocubes, nanorods, and nanoparticles) were synthesized and used as supports to evaluate the support morphology-dependent ammonia synthesis activity in the structure-sensitive ammonia synthesis reaction. The Ru/r-CeO2 catalyst shows a higher catalytic reaction rate (3830 mu mol g(-1) h) than that of Ru/c-CeO2 (1289 mu mol g(-1) h) and Ru/p-CeO2 (529 mu mol g(-1) h) under the reaction conditions of 400 degrees C, 1 MPa, and 60 mL min(-1). In addition, promoters (Cs, K, and Ba) can effectively enhance the catalytic activity of the catalysts such as 2Cs-Ru/r-CeO2 (14 266 mu mol g(-1) h) and 2K-Ru/r-CeO2 (11227 mu mol g(-1) h). The effect of the morphology of the CeO2 support on the metal-support interaction and catalytic performance of the Ru/CeO2 catalysts can be correlated to the exposed crystal planes and surface composition/electronic structure of the CeO2 support with diverse morphologies.