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Abstract

A zirconium oxynitride catalyst was used for the decomposition of ammonia to hydrogen and nitrogen. The onset of catalytic activity at 550 °C coincided with the onset of nitrogen ion mobility in the material and a phase change from the initial β′ phase ( Zr7O11N2) to the nitrogen-rich β″ ZrON phase ( Zr7O9,5N3). No hydrazine formation during an extended time on stream was detectable. Moreover, the onset of activity was also correlated to a rapid change in the electronic structure of the surface accompanying formation of the more active β″ ZrON phase. The results presented here show for the first time a direct correlation among the onset of ion conductivity as a bulk property, a modified electronic structure of the surface, and the catalytic performance of a heterogeneous catalyst.