Promoted Ru/C catalysts for decomposition of ammonia are incorporated into micro-fabricated reactors for the first time. With the reported preparation technique, the performance is increased more than two orders of magnitude compared to previously known micro-fabricated reactors for ammonia decomposition. The catalytic activities for production of hydrogen from ammonia are determined for different promoters and promoter levels on graphite supported ruthenium catalysts. The reactivity trends of the Ru/C catalysts promoted with Cs and Ba are in excellent agreement with those known from earlier studies of both ammonia synthesis and decomposition, and it is shown how proper promotion can facilitate ammonia decomposition at temperatures below 500 K.