Evolution of amorphous ruthenium nanoclusters into stepped truncated nano-pyramids on graphitic surfaces boosts hydrogen production from ammonia

Chen, Yifan; Young, Benjamin J.; Aliev, Gazi N.; Kordatos, Apostolos; Popov, Ilya; Ghaderzadeh, Sadegh; Liddy, Thomas J.; Cull, William J.; Kohlrausch, Emerson C.; Weilhard, Andreas; Hutchings, Graham J.; Besley, Elena; Theis, Wolfgang; Alves Fernandes, Jesum; Khlobystov, Andrei N.

Abstract

Atomic-scale changes can significantly impact heterogeneous catalysis, yet their atomic mechanisms are challenging to establish using conventional analysis methods. By using identical location scanning transmission electron microscopy (IL-STEM), which provides quantitative information at the single-particle level, we investigated the mechanisms of atomic evolution of Ru nanoclusters during the ammonia decomposition reaction. Nanometre-sized disordered nanoclusters transform into truncated nano-pyramids with stepped edges, leading to increased hydrogen production from ammonia. IL-STEM imaging demonstrated coalescence and Ostwald ripening as mechanisms of nanocluster pyramidalization during the activation stage, with coalescence becoming the primary mechanism under the reaction conditions. Single Ru atoms, a co-product of the catalyst activation, become absorbed by the nano-pyramids, improving their atomic ordering. Ru nano-pyramids with a 2–3 nm2 footprint consisting of 3–5 atomic layers, ensure the maximum concentration of active sites necessary for the rate-determining step. Importantly, the growth of truncated pyramids typically does not exceed a footprint of approximately 4 nm2 even after 12 hours of the reaction, indicating their high stability and explaining ruthenium's superior activity on nanotextured graphitic carbon compared to other support materials. The structural evolution of nanometer-sized metal clusters with a large fraction of surface atoms is qualitatively different from traditional several-nm nanoparticles, where surface atoms are a minority, and it offers a blueprint for the design of active and sustainable catalysts necessary for hydrogen production from ammonia, which is becoming one of the critical reactions for net-zero technologies.

Citation

Chen, Y., Young, B. J., Aliev, G. N., Kordatos, A., Popov, I., Ghaderzadeh, S., Liddy, T. J., Cull, W. J., Kohlrausch, E. C., Weilhard, A., Hutchings, G. J., Besley, E., Theis, W., Alves Fernandes, J., & Khlobystov, A. N. (2025). Evolution of amorphous ruthenium nanoclusters into stepped truncated nano-pyramids on graphitic surfaces boosts hydrogen production from ammonia. Chemical Science, 16(6), 2648-2660. https://doi.org/10.1039/d4sc06382a

• Journal Article Type: Article
• Acceptance Date: Nov 22, 2024
• Online Publication Date: Jan 9, 2025
• Publication Date: Jan 9, 2025
• Deposit Date: Mar 29, 2025
• Publicly Available Date: Mar 31, 2025
• Journal: Chemical Science
• Print ISSN: 2041-6520
• Electronic ISSN: 2041-6539
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 16
• Issue: 6
• Pages: 2648-2660
• DOI: https://doi.org/10.1039/d4sc06382a
• Public URL: https://nottingham-repository.worktribe.com/output/44078032
• Publisher URL: https://pubs.rsc.org/en/content/articlelanding/2025/sc/d4sc06382a