A Comprehensive Review on Hydrogen Production via Catalytic Ammonia Decomposition

A comprehensive literature review highlights how the nature of active metals, support materials, promoters, and synthesis methods influences catalytic performance, with particular attention to ruthenium-based catalysts as the current benchmark. Kinetic models are presented to describe the reaction pathway and predict catalyst behavior. Various reactor configurations, including fixed-bed, membrane, catalytic membrane, perovskite-based, and microreactors, are evaluated in terms of their suitability for ammonia decomposition. While ruthenium remains the benchmark catalyst, alternative transition metals such as iron, nickel, and cobalt have also been investigated, although they typically require higher operating temperatures (≥500 °C) to achieve comparable conversion levels. At the industrial scale, catalyst development must balance performance with cost. Inexpensive and scalable materials (e.g., MgO, Al₂O₃, CaO, K, Na) and simple preparation techniques (e.g., wet impregnation, incipient wetness) may offer lower performance than more advanced systems but are often favored for practical implementation. From a reactor engineering standpoint, membrane reactors emerge as the most promising technology for combining catalytic reaction and product separation in a single unit operation. This review provides a critical overview of current advances in ammonia decomposition for hydrogen production, offering insights into both catalytic materials and reactor design strategies for sustainable energy applications.