Catalyst for hydrogen from ammonia gets more active over time

This is the claim of a research team from Nottingham University's School of Chemistry that has developed a novel material consisting of nanosized ruthenium (Ru) clusters attached to graphitised carbon. Developed in collaboration with Birmingham and Cardiff Universities, the Ru nanoclusters react with ammonia molecules, splitting them into hydrogen and nitrogen. The team’s findings are detailed in Chemical Science.

With high volumetric energy density, ammonia is said to hold promise as a zero-carbon energy carrier, so 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, so understanding the atomic-level mechanisms behind changes in the catalyst activity is critical for designing the next generation of heterogeneous catalysts.

In a statement, Dr Jesum Alves Fernandes, an Associate Professor in Nottingham’s School of Chemistry, and co-leader of the research team, said: “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 2-3nm-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.”