Researchers have developed a new catalyst that uniquely increases in activity over time, unlike most that degrade.
This self-improving catalyst, made of ruthenium on a carbon base, offers a sustainable pathway to split ammonia into hydrogen, a clean energy carrier.
Revolutionary Hydrogen Production from Ammonia
Scientists have developed a groundbreaking catalyst for generating hydrogen from ammonia that becomes more effective with continued use. By analyzing the atomic structure, they identified key changes that enhance its performance over time.
A collaborative team from the University of Nottingham’s School of Chemistry, along with researchers from the University of Birmingham and Cardiff University, created a novel material made of nanosized ruthenium (Ru) clusters embedded in graphitized carbon. These Ru nanoclusters react with ammonia, catalyzing its breakdown into hydrogen and nitrogen — a crucial step toward producing green hydrogen. This innovative work is detailed today (January 9) in Chemical Science, the flagship journal of the Royal Society of Chemistry.
Enhancing Catalyst Performance Through Atom-Level Control
With its high volumetric energy density, ammonia holds promise as a zero-carbon energy carrier that could drive a sustainable new economy in the near future. Finding fast and energy-efficient methods to crack ammonia into hydrogen (H₂) and nitrogen (N₂) on demand is essential. While catalyst deactivation is common, it is rare for a catalyst to become more active with use. Therefore, understanding the atomic-level mechanisms behind changes in the catalyst activity is critical for designing the next generation of heterogeneous catalysts.
Dr. Jesum Alves Fernandes, an Associate Professor in the School of Chemistry, University of Nottingham, and co-leader of the research team, explained: “Traditional catalysts consist of nanoparticles, with most atoms inaccessible for reactions. Our approach starts with individual atoms that self-assemble into clusters of a desired size. Therefore, we can halt the growth of the clusters when their footprints reach 2-3 nm-squared, ensuring that the majority of atoms remain on the surface and available for chemical reactions. In this work, we harnessed this approach to grow ruthenium nanoclusters from atoms directly in a carbon support.”
Innovative Techniques for Catalyst Development
The researchers employed magnetron sputtering to generate a flux of metal atoms for constructing the catalyst. This solvent- and reagent-free technique enables the fabrication of a clean, highly active catalyst. By maximizing the catalyst’s surface area, this method ensures the most efficient use of rare elements like ruthenium (Ru).
Dr. Yifan Chen, a Research Fellow at the University of Nottingham’s School of Chemistry, said: “We were surprised to discover that the activity of Ru nanoclusters on carbon actually increases over time, which defies deactivation processes typically taking place for catalysts during their usage. This exciting finding cannot be explained through traditional analysis methods, and so we developed a microscopy approach to count the atoms in each nanocluster of the catalyst through different stages of the reaction using scanning transmission electron microscopy. We revealed a series of subtle yet significant atomic-level transformations.”
Groundbreaking Findings and Future Implications
Researchers discovered that ruthenium atoms initially disordered on the carbon surface rearrange into truncated nano-pyramids with stepped edges. The nano-pyramids demonstrate remarkable stability over several hours during the reaction at high temperatures. They continuously evolve to maximize the density of active sites, thereby enhancing hydrogen production from ammonia. This behavior explains the unique self-improving characteristics of the catalyst.
Professor Andrei Khlobystov, School of Chemistry, University of Nottingham, said: “This discovery sets a new direction in catalyst design by showcasing a stable, self-improving system for hydrogen generation from ammonia as a green energy source. We anticipate this breakthrough will contribute significantly to sustainable energy technologies, supporting the transition to a zero-carbon future.”
This invention marks a major advancement in understanding the atomistic mechanisms of heterogeneous catalysis for hydrogen production. It paves the way for developing highly active, stable catalysts that use rare metals sustainably by precisely controlling catalyst structures at the nanoscale.
The University of Nottingham is dedicated to championing green and sustainable technologies. The Zero Carbon Cluster has been recently launched in the East Midlands to accelerate the development and deployment of innovation in green industries and advanced manufacturing.
Reference: “Evolution of amorphous ruthenium nanoclusters into stepped truncated nano-pyramids on graphitic surfaces boosts hydrogen production from ammonia” 9 January 2025, Chemical Science.
This work is funded by the EPSRC Programme Grant ‘Metal atoms on surfaces and interfaces (MASI) for sustainable future’ which is set to develop catalyst materials for the conversion of three key molecules – carbon dioxide, hydrogen, and ammonia – crucially important for the economy and environment. MASI catalysts are made in an atom-efficient way to ensure sustainable use of chemical elements without depleting supplies of rare elements and making most of the earth’s abundant elements, such as carbon and base metals.
