Effects of support and promoter on Ru catalyst activity in microwave-assisted ammonia synthesis

[Display omitted] •Microwave-assisted catalytic process is a promising alternative for NH3 synthesis.•The Ru electronic and geometric structures are affected by support and promoter.•Ru on CeO2 support was more active than that on MgO support.•Lower electronegativity of Cs promoter result in higher activity of Ru.•The reaction mechanisms were investigated using DFT calculations. Microwave-assisted ammonia synthesis is a promising alternative to the energy-intensive Haber-Bosch process, specially at small- and medium-scale with renewable H2 as resource. Here, we report that Cs promoted Ru/CeO2 catalyst exhibits considerable activity at 533 K and ambient pressure. In this work, the combined theoretical and experimental approaches are adopted to optimize the electronic and geometric structures of Ru on the catalysts. Both DFT modeling work and structural characterization show that the strong interaction between Ru and CeO2 results in the formation of highly dispersed Ru particles favoring ammonia synthesis. The higher electron donating ability of CeO2 and lower electronegativity of Cs promoter result in higher electron density on Ru reducing the N≡N dissociation barrier. The work demonstrates the potential of microwave-assisted catalytic process in activating stable molecules for ammonia synthesis.