Robust Ru single-atom alloy catalysts coupled with adjacent Fe-site for highly stable ammonia synthesis under mild conditions

• Published in: Applied surface science 2025-03, Vol.685, p.161906, Article 161906
• Main Authors: Singh, Swati, Komarala, Eswaravara Prasadarao, Kim, Seok-Jin, Yavuz, Cafer T., Maghrabi, Louai Mahdi, Singh, Nirpendra, Harfouche, Messaoud, Sabastian, Victor, Malina, Ondrej, Bakandritsos, Aristides, Anjum, Dalaver Hussain, AlHammadi, Ali Abdulkareem, Polychronopoulou, Kyriaki
• Format: Article
• Language: English
• Subjects: Ammonia synthesis; DFT; Layered double hydroxide-derived support; Mössbauer spectroscopy; Ruthenium; Single atom alloy catalyst; Synchrotron EXAFS
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2024.161906

[Display omitted] •Ru single-atom alloy catalysts on MgFe LDH-derived supports for NH3 synthesis.•The 0.1 wt% Ru loading enhanced catalytic performance and stability for 150 h.•Synchroton EXAFS confirms the Ru-Fe single-atom alloy formation.•Ru single atom weakens N2 binding and facilitating intermediates desorption (DFT).•NH3 synthesis rate per Ru loading is almost 20 times higher than reported values. In our pursuit of an efficient catalyst for ammonia production, we developed ruthenium (Ru)-based single atom alloy catalysts on a layered double hydroxide-derived support. The extended X-ray absorption fine structure studies provided evidence of single Ru atoms as a Fe-Ru alloy. High-resolution transmission electron microscopy showcased a larger particle size with higher Ru loading, emphasizing the role of Ru site geometry in catalytic activity. The MgFeOx-0.1Ru catalyst, with optimal Ru dispersion and smaller Fe-Ru particle size (1.6 nm), outperformed other catalysts in NH3 synthesis and demonstrated exceptional stability. Remarkably, the catalyst with 0.1 wt% Ru exhibited superior performance, achieving an exceptional NH3 formation rate of 17,897 µmol g−1 h−1 (at 400 °C, 5 MPa, and Weight hourly space velocity (WHSV) of 50,000 mL g−1 h−1) along with maintaining a consistent NH3 synthesis rate of 7,217 µmol g−1 h−1 (at 400 °C, WHSV of 10,000 mL g−1 h−1, and 5 MPa), for a notable duration of 150 h. Our first-principles calculations show that Ru weakened the binding of both molecular and atomic nitrogen on the catalyst’s surface, facilitating the desorption of N-intermediates. The optimized MgFeOx-0.1Ru catalyst composition with characteristics such as small Fe-Ru alloy particle size and the presence of all active Ru sites on the surface improves lifetime, reducing costs and marking a significant stride towards sustainable and economically viable NH3 production.