(698f) Investigation of Shaped Supports for Ruthenium-Based Catalysts on Ammonia Synthesis

Ammonia is necessary to produce synthetic fertilizer and has recently been suggested as a carbon-free energy carrier. Industrial ammonia production utilizes the Haber-Bosch method, which uses iron as an active metal and requires large energy input¹. Ruthenium-based materials are considered a possible alternative. However, many investigations into various variables including supports, and morphology effects, are needed to improve these catalysts to compete with current industrial catalysts^1,2. Utilizing different supports, such as praseodymium oxide may enhance the high dispersion of metal atoms and the number of active sites³. Moreover, synthesizing different shapes of nanoparticles with different faceting is one method to increase the catalytic activity of a catalyst^2,3.

In this work, praseodymium oxide (Pr_xO_y) nanowires and nanospheres were synthesized using the hydrothermal and precipitation methods, respectively. Ruthenium (Ru) with the different weight loadings were deposited onto the synthesized supports using simple impregnation method. Ru/Pr_xO_y nanowires catalysts showed higher activity compared to nanospheres catalysts. Moreover, the activity of the Ru/Pr_xO_y nanowires catalysts that were calcined at lower temperature, was higher because of different surface area and pore volume. Characterization using HRTEM, physisorption, chemisorption, CO-DRIFTS and XRD were used to investigate the differences between nanowires and nanospheres catalysts and the effects of morphology on ammonia synthesis rate. Well-known ammonia synthesis promoters, such as cesium and barium, were added to all the catalysts to increase the catalytic activity.

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3. Chen, N., Younis, A., Chu, D. & Li, S. Controlled fabrication of Pr(OH)3 nanowires for enhanced photocatalytic activities. J. Rare Earths 37, 60–67 (2019).