Mechanistic Insights Into Nickel-Based Catalysts for Ammonia Decomposition Toward Efficient Hydrogen Generation.

Ammonia is emerging as a carbon-free hydrogen carrierowing to its high hydrogen density, established storage infrastructure, and compatibility with existing energy carriers. Nevertheless, the efficient release of hydrogen through ammonia decomposition at low temperatures remains kinetically demanding. This review provides a comprehensive overview of recent advances in nickel-based catalysis for ammonia decomposition, emphasizing the interplay between catalyst design, mechanistic understanding, and performance optimization guided by the Sabatier principle. The discussion highlights how basic and defect-rich oxide supports (CeO2, La2O3, Gd-CeO2) enhance Ni dispersion and electronic interactions, promoting activity rivaling that of noble metals. The incorporation of rare-earth and alkaline-earth promoters (Ce, La, Mg) improves low- and high-temperature stability, while bimetallic systems such as Ni-Co and Ni-Fe alloys extend the operational temperature window and activity range through synergistic effects. Emerging insights from atomic-scale catalysts, including single Ni sites on reducible oxides, reveal pathways to lower activation barriers and enable ammonia decomposition near 300°C. Collectively, this review consolidates mechanistic advances and engineering strategies that unify surface science, materials chemistry, and reactor design, providing a framework for developing cost-effective, durable, and low-temperature Ni-based catalysts for efficient hydrogen generation from ammonia.