Ru/MgO Catalysts Modified with Various Alkali Metals (Na, Cs, K) for CO_<i>x</i>-Free H₂ Production from NH₃ Decomposition

Developing low-temperature, high-efficiency ammonia decomposition catalysts for hydrogen production is essential for the broad application of hydrogen. This study conducted a systematic investigation of Ru/MgO catalysts modified with different alkali metals (Na, K, Cs), unveiling the impact of these modifications on catalyst performance and developing a highly efficient low-temperature ammonia decomposition catalyst. The addition of all alkali metals enhances the catalytic performance of Ru/MgO for ammonia decomposition, especially the addition of K, which results in the optimal enhancement of the catalyst, achieving a 75% ammonia decomposition efficiency at 350 °C (GHSV= 2,000 mL/h·gcat), more than doubling the performance of the unmodified Ru/MgO catalyst. The study revealed that the addition of potassium (K) altered the rate-determining step of the ammonia decomposition reaction from nitrogen recombination to the dissociation of the first hydrogen atom, and reduced the overall energy barrier required for the reaction. This facilitated the desorption of nitrogen from the Ru surface and the conversion of NH3, thereby accelerating the rate of the ammonia decomposition reaction.