(111d) Investigation of the Dual-Site Nitride Catalyst in Ammonia Decomposition

With the sustainable development of human society, clean and sustainable energy sources play an increasingly important role. Hydrogen energy, with its environmental-friendly nature, abundant reserves and high utilization efficiency, is considered as an extremely promising energy carrier. However, hydrogen is difficult to store in liquid phase at room temperature and pressure, and usually relies on other substances as carriers. Ammonia, composed of only N and H, is an ideal hydrogen energy vector with high hydrogen storage density, while it can be efficiently converted to H₂ without CO_x emission. Therefore, the ammonia decomposition reaction plays a significant role in achieving the release and utilization of hydrogen energy. Ammonia decomposition is an endothermic reaction, and the decomposition of ammonia into H₂ is thermodynamically preferable above 400 °C. However, the kinetics of this process are relatively slow due to the high energy barriers for NH₃ activation and N₂ desorption, which has prompted research into efficient catalysts for ammonia decomposition. However, breaking the scaling relationship between NH₃ activation and N₂ desorption is a critical challenge and the single active site fails to decouple these processes. In this study, a novel Ni-based dual-site nitride catalyst was synthesized by the induction of alkali metals and used in the ammonia decomposition process. This catalyst shows high-efficient performance for ammonia decomposition as it can achieve N-H bond activation and N-N bond recombination in different regions. The structure of the dual active sites was precisely constructed and identified, and its reaction mechanism was investigated by abundant in situ characterization techniques. This approach provides a new insight for constructing novel ammonia decomposition catalysts.