Efficient catalytic ammonia synthesis using Cs-doped Ru/ZrO2 catalysts prepared via a low eutectic system

This study explores the preparation of a Cs-doped Ru/ZrO 2 catalyst using a low eutectic system and its application in ammonia synthesis. Additionally, it examines the effect of Cs doping on enhancing the catalyst's resistance to hydrogen poisoning. Compared to the undoped Ru/ZrO 2 catalyst and the Cs–Ru/ZrO 2 –B catalyst prepared through the grinding method for promoter incorporation, the Cs–Ru/ZrO 2 -A catalyst synthesized using the low eutectic system demonstrated significantly enhanced activity. At 400 °C and 0.1 MPa, the Cs–Ru/ZrO 2 -A catalyst achieved an ammonia synthesis activity of 1769 μmol g cat −1  h −1 , which is approximately 35 times higher than that of the undoped Ru/ZrO 2 catalyst. The structure of the catalyst was analyzed using various material characterization techniques, including XRD, XPS, and SEM. The results showed that the Cs–Ru/ZrO 2 -A catalyst, prepared under identical conditions, exhibited no significant structural differences compared to other catalysts. However, further TPR and TPD analyses revealed that Cs interacts with Ru to some extent, affecting its reduction behavior and enhancing the catalytic reaction rate for ammonia synthesis. Additionally, detailed XPS analysis of all catalysts was conducted, leading to a proposed relationship between the catalytic reaction rate and the oxidation states of the metal components. The study revealed that the presence of Cs significantly inhibits hydrogen poisoning of the catalyst. Furthermore, it demonstrated that the addition of promoters enhances H 2 dissociation by supplying electrons to the active metal Ru, while Cs plays a crucial role in effectively suppressing hydrogen poisoning.