Facile formation of barium titanium oxyhydride on a titanium hydride surface as an ammonia synthesis catalyst.

Oxyhydrides are promising compounds as supports for ammonia synthesis catalysts because they suppress hydrogen poisoning on the catalyst surface and enhance the ammonia synthesis activity. Herein, we developed a facile method for preparing BaTiO2.5H0.5, a perovskite oxyhydride, on a TiH2 surface via the conventional wet impregnation method using TiH2 and Ba hydroxide. Scanning electron microscopy and high-angle annular dark-field scanning transmission electron microscopy observations revealed that BaTiO2.5H0.5 crystallized as nanoparticles of ca. 100-200 nm on the TiH2 surface. The Ru-loaded catalyst Ru/BaTiO2.5H0.5-TiH2 exhibited 2.46 times higher ammonia synthesis activity (3.05 mmol-NH3 g-1 h-1 at 400 °C) than the benchmark Ru catalyst Ru-Cs/MgO (1.24 mmol-NH3 g-1 h-1 at 400 °C) because of the suppression of hydrogen poisoning. The analysis of reaction orders showed that the effect of suppressing hydrogen poisoning on Ru/BaTiO2.5H0.5-TiH2 was equivalent to that of the reported Ru/BaTiO2.5H0.5 catalyst, thus supporting the formation of BaTiO2.5H0.5 perovskite oxyhydride. This study demonstrated that the selection of appropriate raw materials facilitates the formation of BaTiO2.5H0.5 oxyhydride nanoparticles on the TiH2 surface using the conventional synthesis method.

Method for evaluating the performance of catalytic reactions using renewable-energy-derived materials.

Hydrogen produced by electrolysis using electricity derived from renewable energy sources has a fluctuating supply. However, conventional catalyst evaluation methods cannot evaluate catalyst synthesis assuming a fluctuating feedstock. This paper investigates a simple screening method for catalysts that can be used for renewable energy by using a combination of three catalyst evaluation methods: Light-off Performance, equilibrium achievement degree, and maximum ammonia concentration. We examined the combination of evaluation methods and trends for each element, and finally concluded that a three-axis graph combining the three is the easiest graph to obtain the information necessary for catalyst screening intuitively rather than quantitatively.

Enhanced ammonia synthesis activity of Ru-supported cerium-lanthanum oxide induced by Ti substitution forming mesopores.

Ru/Ce0.5La0.5-xTixO1.75+0.5x solid solutions with cubic fluorite structure were successfully synthesized via the polymerized complex method. While the Ti substitution enhanced Ce4+ reducibility by compensating for oxygen vacancies, the reducibility showed no correlation with ammonia synthesis activity. However, Ru/Ce0.5La0.4Ti0.1O1.8 showed the highest activity originating from the facilitated formation of mesopores.

The effect of a ruthenium precursor on the low-temperature ammonia synthesis activity over Ru/CeO2.

Catalysts supported on CeO2 were prepared using various Ru precursors. The H2-TPR profile of the catalyst was obtained beginning at -70 °C for the first time, and a previously unreported reduction peak was observed at approximately 50 °C. The lower peak temperature was associated with a higher ammonia synthesis activity.