Transforming ladle furnace slag into an efficient catalyst for hydrogen production by ammonia decomposition

Ladle furnace slag (LFS), a byproduct of steel production, was modified via HCl treatment and calcination to obtain an efficient catalyst for ammonia decomposition. The unmodified catalyst (LFS-C500) and its modified counterpart (MLFS-C500) were thoroughly characterized by a combination of techniques, including temperature programmed reduction (TPR), X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX), and X-ray fluorescence (XRF). MLFS-C500 outperformed LFS-C500, achieving 96.3% ammonia conversion at 700 °C and a space velocity of 6 000 ml NH₃/(h × gcat), with a lower activation energy (131.7 kJ/mol) compared to LFS-C500 (153.0 kJ/mol). The superior performance of MLFS-C500 is attributed to its higher iron content, which successfully forms Fe crystallites upon reduction in H2, and its enhanced surface structure, resulting from the removal of calcium compounds upon HCl modification. This work demonstrates how an industrial waste can be effectively valorised into low-cost catalysts for COx-free hydrogen production.