Cluster size effects on hydrazine decomposition on Irn/Al2O3/NiAl(1 1 0)

A series of planar model catalysts were prepared by deposition of size-selected on Al₂O₃/NiAl(1 1 0), and hydrazine decomposition chemistry was used to probe their size-dependent chemical properties. Small Ir_n (n ? 15) on Al₂O₃/NiAl(1 1 0) are able to induce hydrazine decomposition at temperatures well below room temperature, with significant activity first appearing at Ir₇. Both activity and product branching are strongly dependent on deposited cluster size, with these small clusters supporting only the simplest decomposition mechanism: dehydrogenation and N₂ desorption at low temperatures, followed by H₂ recombinative desorption at temperatures above 300 K. For Ir₁₅, we begin to see ammonia production, signaling the onset of a transition to clusters able to support more complex chemistry.