Catalytic Ammonia Decomposition for COx-Free Hydrogen Production over Fumed SiO₂-Supported Co–Ni Bimetallic Catalysts

Hydrogen production from ammonia decomposition using cheap metal catalysts at moderate temperatures is facing challenges. In this study, a fumed SiO2-supported Co–Ni bimetallic catalyst (Co9Ni1/SiO2) was prepared by coimpregnation. The catalyst achieved a 99.55% NH3 conversion and a 55.99 mmol gcat–1 h–1 H2 yield at 550 °C with a w8 hly space velocity (WHSV) of 30,000 mL gcat–1 h–1. Besides, the catalyst exhibited good stability and reproducibility during a 60 h continuous test at 500–550 °C. XRD and TEM results confirmed that Co and Ni were well dispersed on the catalyst surface and exhibited a strong synergistic effect. Kinetic tests showed that the bimetallic Co–Ni catalyst effectively reduced the apparent activation energy of the ammonia decomposition reaction compared to monometallic Co or Ni catalysts. This study provides a new case for designing and developing efficient and cheap catalysts for ammonia decomposition.