Light metal amides and imides are a new class of highly active ammonia decomposition catalysts. Indeed, composites of lithium imide and transition metal nitrides are likely to surpass optimised ruthenium-based catalysts. Significantly, these low-cost catalysts function by bulk reaction and represent a departure from conventional surface catalysis. Understanding these novel bulk mechanisms is crucial for further advances to be made in the development of these catalysts which, in turn, will facilitate sustainable energy provision from ammonia. We request 4 days on POLARIS to conduct an in situ structural investigation on two composite lithium imide ? metal nitride ammonia decomposition catalysts, one with manganese nitride and one with iron nitride. In particular, we wish to probe the active form of the catalyst materials, determining whether a ternary nitride is formed.