Efficient Low-temperature Ammonia Cracking Enabled by Strained Heterostructure Interfaces on Ru-free Catalyst

Abstract

Ammonia (NH₃) has emerged as a promising liquid carrier for hydrogen (H₂) storage. However, its widespread adoption in H₂ technology is impeded by the reliance on costly Ru catalysts for low-temperature NH₃ cracking reaction. Here, a strained heterostructure Co@BaAl₂O_4−x core@shell catalyst is reported that demonstrates catalytic performance at low reaction temperatures comparable to most Ru-based catalysts. This catalyst exhibits exceptional activity across a range of space velocity conditions, maintaining high conversion rates at 475 to 575 °C and achieving an impressive H₂ production rate of 64.6 mmol H₂ g_cat⁻¹ min⁻¹. Synchrotron X-ray absorption spectroscopy, synchrotron X-ray diffraction, and kinetic studies are carried out to elucidate the dynamic changes of the strained heterostructure interface of Co-core and BaAl₂O_4−x-overlayer under catalytic working conditions. The performance enhancement mechanisms are attributed to the tensile strained Co surface encapsulated in the defective BaAl₂O_4−x, which enhances NH₃ adsorption and facilitates the rate-determining N─H dissociation. Furthermore, the strain release and restoration during NH₃ dehydrogenation enable efficient nitrogen desorption, preventing active site poisoning. This work highlights the effectiveness of lattice strain engineering and the development of synergistic strong metal-support interfaces between active metal nanoparticles and oxide support to boost low-temperature NH₃ cracking.