Short summary: Approximately 85% of globally synthesized ammonia, produced via the Haber–Bosch process, is used in the manufacture of synthetic fertilizers, making it essential for modern agriculture. Conventional ammonia synthesis relies on iron-based catalysts and, more recently, costly ruthenium-based catalysts operating at high temperatures (300–500 °C) and pressures (50–200 bar).

Magnetic heating has recently emerged as a promising alternative for catalytic processes, enabling localized heating of magnetic nanoparticles. In this work, Co₀.₆₇Ni₀.₃₃ alloy nanoparticles decorated with cerium(IV) oxide nanoparticles (Co–Ni@CeO₂) were investigated as potential magnetic catalysts for ammonia synthesis. The catalysts were prepared using the Pechini sol–gel method, followed by reductive heat treatment. The effects of citric acid concentration and reduction temperature on the magnetic and catalytic properties of the nanocomposites were systematically studied. The Co–Ni@CeO₂ catalyst was evaluated under ammonia synthesis conditions at different reaction temperatures in an alternating magnetic field.