Ammonia, a liquid at modest conditions, is a leading carrier for hydrogen transportation and storage. Low temperature decomposition and purification is required for efficient on site and on demand deployment. Supported ruthenium catalysts are state-of-the-art for low temperature ammonia decomposition; however, they are costly. We are developing supported Ni catalysts as cost effective alternatives. In this work physi- and chemi-sorption were used in conjunction with (S)TEM and hydrogen temperature programmed reduction to determine specific and active surface areas, crystallite size, metal dispersion and mechanistic insights for a number of catalysts. Measurements of catalyst composition and structure are correlated with catalyst activity quantified in a flow reactor as a function of temperature , pressure, and composition. First a series of commercial Ru catalysts were compared and unsurprisingly performance was most strongly correlated with metal dispersion. With this baseline understanding these tools were applied to understand a nickel catalyst formed by auto-combustion synthesis to form NiLaO3 perovskite which was subsequently reduced to form Ni-La2O3 catalyst. Various synthesis parameters were varied, including fuel identity, reactant ratios, intermediate processing, calcination temperature, and reduction conditions, to find the combination that maximized desired properties. The Ni/La2O3 catalysts display high activity at low temperature, with rates approaching that of the Ru benchmark. Among process variables calcination temperature reduction temperature, and fuel choice had the most significant impact on surface area and reactivity. In this presentation we further elaborate on the specific process-structure-property-performance relationships in this system and use these insights to pursue additional strategies to further increase the performance of earth-abundant catalysts for hydrogen production from ammonia.
