Nitrogen Plasma-Induced Interface Reconstruction Boosting Hydrogen Production Performance of Cobalt-Based Catalysts in Ammonia Decomposition

A key issue with conventional cobalt-based catalysts in ammonia decomposition is the aggregation and sintering of active sites under high-temperature conditions, leading to rapid deactivation. Here, we discovered that the performance of the Co/Al2O3 catalyst was significantly enhanced through nitrogen plasma pretreatment. At a reaction temperature of 600 °C, the hydrogen production rate of the catalyst increased by 22% after 25 W plasma treatment compared to the untreated sample, while its apparent activation energy also decreased significantly (from 66.1 ± 1.2 to 48.6 ± 2.9 kJ/mol). Regarding stability, after 40 h of testing at 600 °C, the catalyst maintained 76% ammonia conversion, demonstrating excellent stability. To investigate the underlying cause of this performance enhancement, characterization revealed that pretreatment induced the formation of the CoAl2O4 spinel phase. This phase optimized the electronic structure and spatial distribution of active sites, thereby enhancing intrinsic activity. Characterization results further confirmed that this treatment effectively suppressed sintering of the active components at high temperatures, removed impurities from the pore channels, and strengthened metal–support interactions. This was manifested in an improved cobalt dispersion, increased CoAl2O4 crystallinity, and enhanced surface reducibility. Therefore, this study demonstrates that nitrogen plasma pretreatment is an effective strategy for preparing high-performance ammonia decomposition catalysts through interfacial restructuring.