Enhanced ammonia decomposition activity through K-promoted interaction between Co2MgO4 and carbon nanotube

Developing efficient non-noble-metal catalysts for ammonia decomposition requires coordinated control of the active metal and its local surface environment. Here, a Co–Mg/CNT catalyst series was constructed to examine the effects of CNT surface treatment, K promotion, and Co/Mg composition. Pristine, acid-washed, and K-modified CNTs were used as supports, and the resulting catalysts were evaluated by structural characterization, H 2 -TPR, CO 2 -TPD, NH 3 -TPSR, and catalytic testing. CNT incorporation increased accessible surface area and altered the distribution and reduction behavior of Co-containing species, while acid washing and K modification shifted the first H 2 -TPR reduction maximum to lower temperatures. K-containing catalysts also showed stronger basic-site signatures and enhanced low-temperature NH 3 responses. Among the tested catalysts, Co 3 Mg/K-CNT exhibited the highest low-temperature activity, reaching about 85% NH 3 conversion at 450 °C despite having a lower BET surface area than Co 2 Mg/K-CNT. It also showed the lowest apparent activation energy of 22.0 kJ mol −1 and maintained approximately 98% NH 3 conversion at 500 °C for 90 h. These results indicate that catalytic performance is governed by the coupled effects of support surface chemistry, K promotion, and Co/Mg composition.