Agglomeration-Resistant\nNi Nanoparticles Generated\nby <i>In Situ</i> Hydrogenation Treatment of LaNiO<sub>3</sub> as Catalyst for the Ammonia Decomposition

The development of low-temperature, nonprecious metal\nthermocatalysts\nfor ammonia decomposition holds significant promise for advancing\nthe green hydrogen industry. LaNiO<sub>3</sub> catalysts, with their\nperovskite structure (ABX<sub>3</sub>), are notable for enabling <i>in situ</i> growth of active metal Ni on reduced oxide supports\nduring ammonia decomposition reactions (ADRs). However, unintentional <i>in situ</i> growth can lead to uncontrolled reactions and metal particle agglomeration.\nTo address this, we employed a straightforward high-temperature and\npressure hydrogenation pretreatment process to enhance the interaction\nbetween the active metal and the support, thereby suppressing the\nagglomeration of the active metal during the ADR process. Our results\nindicate that the hydrogenation pretreatment catalyst exhibits finer\nNi metal nanoparticles, with an average size of approximately 8 nm.\nUnder a gas hourly space velocity (GHSV) of 18,000 mL g<sub>cat</sub><sup>–1</sup> h<sup>–1</sup> and at 550 °C, the\nNH<sub>3</sub> conversion efficiency reaches 90%, which exhibited\nexcellent stability over a period of 100 h. Additionally, we utilized\nTEM, XPS, EPR, NH<sub>3</sub>-TPD, and H<sub>2</sub>-TPR techniques\nto elucidate the intrinsic mechanisms related to the enhanced catalytic\nactivity. This study addresses the issue of active metal nanoparticle\nagglomeration through hydrogenation pretreatment.