Agglomeration-Resistant Ni Nanoparticles Generated by In Situ Hydrogenation Treatment of LaNiO₃ as Catalyst for the Ammonia Decomposition

The development of low-temperature, nonprecious metal thermocatalysts for ammonia decomposition holds significant promise for advancing the green hydrogen industry. LaNiO 3 catalysts, with their perovskite structure (ABX 3 ), are notable for enabling in situ growth of active metal Ni on reduced oxide supports during ammonia decomposition reactions (ADRs). However, unintentional in situ growth can lead to uncontrolled reactions and metal particle agglomeration. To address this, we employed a straightforward high-temperature and pressure hydrogenation pretreatment process to enhance the interaction between the active metal and the support, thereby suppressing the agglomeration of the active metal during the ADR process. Our results indicate that the hydrogenation pretreatment catalyst exhibits finer Ni metal nanoparticles, with an average size of approximately 8 nm. Under a gas hourly space velocity (GHSV) of 18,000 mL g cat –1 h –1 and at 550 °C, the NH 3 conversion efficiency reaches 90%, which exhibited excellent stability over a period of 100 h. Additionally, we utilized TEM, XPS, EPR, NH 3 -TPD, and H 2 -TPR techniques to elucidate the intrinsic mechanisms related to the enhanced catalytic activity. This study addresses the issue of active metal nanoparticle agglomeration through hydrogenation pretreatment.