Metal‐Dependent Support Effects of Oxyhydride‐Supported Ru, Fe, Co Catalysts for Ammonia Synthesis

Abstract

Abstract Ammonia is an attractive energy carrier for the hydrogen economy, given its high hydrogen density and ease of liquefaction. A titanate oxyhydride has recently been demonstrated that can catalyze ammonia synthesis without Ru or Fe metal, despite titanium being regarded as an inert element. Here, the synthesis activity of ammonia is examined when Ru, Fe, and Co particles are supported onto the oxyhydride BaTiO 2.5 H 0.5 . The activity of BaTiO 2.5 H 0.5 as support is significantly higher than BaTiO 3 . For example, the activity for Fe and Co increases by a factor of 70–400, making them more active than Ru/MgO, one conventional Ru catalyst. In terms of mechanism, for Ru, H/D isotope studies show participation of lattice hydride in the catalytic cycle, while kinetic analysis shows reduced H 2 poisoning probably due to spillover. For Fe (and Co), the presence of hydride results in significantly lower activation energy and N 2 reaction order, likely due to strong electron donation from the oxyhydride. This metal‐dependent support effect is further verified by N 2 isotopic exchange experiments. These perovskite‐type oxyhydrides can be easily modified in terms of A ‐ and B ‐site ( A = Ba, B = Ti); the high potential for compositional variation and morphologies will expand the search for efficient catalysts for ammonia synthesis.