Enhanced ammonia decomposition activity over unsupported Co3O4: Unravelling the promotion effect of alkali metal

To deeply understand the effect of alkali metals on the structure-activity relationship of cobalt-based catalysts for ammonia decomposition, unsupported Co3O4 was fabricated as catalyst model. It was found that alkali metals (Na and K) enhanced the NH3 decomposition performance of Co3O4 significantly, with NH3 conversion even higher than supported ones. As indicated by characterizations, appropriate amount of Na doping generated more reducible Co3+, which induced strong interaction with NH3 during reaction. As a result, it was easier for NH3 as well as -NH2 intermediate to dehydrogenate at low temperature. Therefore, the intrinsic activity of Co3O4 for NH3 decomposition was increased. This study not only provided a novel strategy in the practical use of cobalt-based catalysts for NH3 decomposition, but also gave deep insight into the promotion effect of alkali metal.