Ammonia Decomposition over Water‐Durable Hexagonal BaTiO3−xNy‐Supported Ni Catalysts

Abstract Nickel is a promising candidate as an alternative to ruthenium for an ammonia decomposition catalyst. However, the performance of Ni‐based catalysts for ammonia decomposition is still not sufficient to achieve a good hydrogen production rate under low‐temperature because the weak nitrogen affinity of Ni reduces the frequency of the ammonia decomposition reaction. Here, it is reported that Ni supported on barium titanium oxynitride (Ni/ h ‐BaTiO 3− x N y ) with a hexagonal structure acts as a highly active and water‐durable catalyst for ammonia decomposition. The operation temperature is reduced by over 140 °C when N 3− ions are substituted onto the O 2− sites of the BaTiO 3 lattice, and the Ni/ h ‐BaTiO 3− x N y catalyst significantly outperforms conventional oxide‐supported Ni catalysts for ammonia decomposition. Furthermore, the activity of Ni/ h ‐BaTiO 3− x N y remains unchanged after exposure to water. The 15 NH 3 decomposition reaction and Fourier transform‐infrared spectroscopy (FT‐IR) measurements reveal that lattice nitrogen vacancy sites on h ‐BaTiO 3− x N y function as the active sites for ammonia decomposition. The ammonia decomposition activity of Ni/ h ‐BaTiO 3− x N y is also higher than that of the Ni/ h ‐BaTiO 3− x H y oxyhydride catalyst, making a contrast to the activity trend in ammonia synthesis.