Development of highly active Co/Mo2C catalysts for green H2 production from NH3

Abstract

The development of cost-effective catalysts with excellent catalytic performance is of great interest for ammonia cracking. In this work, an innovative and stable cobalt catalyst supported on a commercial molybdenum carbide material was prepared. The influence of pre-activation treatment on the catalytic activity of a 5Co/Mo₂C catalyst for ammonia decomposition was investigated using H₂/Ar and NH₃/Ar at 400 °C. Both activations resulted in a high ammonia conversion (∼ 90 %) at 500 °C. XPS analysis revealed that H₂ pre-activation resulted in greater surface Co/Mo ratio and enhanced charge transfer, contributing to increase active cobalt and hence better catalytic activity. The effect of cobalt loading (2.5–10 wt%) was further optimized, with 7.5Co/Mo₂C achieving the highest conversion (93.7 % at 450 °C), attributed to optimal Co dispersion and crystallite size (∼16.8 nm). The addition of a secondary metal (K, Cs or La) to the 7.5Co/Mo₂C catalyst showed that lanthanum significantly improved the catalytic activity by increasing the basicity, cobalt dispersion, and surface Co/Mo ratio. In contrast, K and Cs had a negative effect, causing agglomeration and reduction of active sites by blocking. These findings indicate that H₂ pre-activation and La promotion were key factors for enhancing ammonia decomposition efficiency on Co/Mo₂C catalyst.