Barium promoted cobalt-cerium catalysts prepared by coprecipitation are efficient and stable at decomposing ammonia. Catalyst with the optimal composition show very similar activity and better stability than benchmark solids containing Ru. Characterization studies reveal that cerium plays a key role as structural promoter, increasing the cobalt dispersion and preventing sintering. These features translate into a very active and stable catalyst. Kinetic analysis shows a decrease in the apparent activation energy upon Ba promotion, and a decrease in the negative hydrogen reaction order, highlighting the role of the alkaline earth metal in alleviating the negative effect of hydrogen and reducing the hydrogenation properties of cobalt, which results in a further improvement of the catalytic activity.