Low Temperature Ammonia Cracking for Hydrogen Production by Layered Double Hydroxide-Based Nickel Catalysts

In this work, various Ni catalysts were tested in the ammonia decomposition for hydrogen generation. Traditional catalyst synthesis methods such as incipient wetness impregnation (IWI), precipitation deposition (PD), wetness impregnation (WI) and commercial catalysts were compared with a Nickel catalyst prepared from a Ni layered double hydroxide (LDH) precursor. The catalysts were characterized by various methods including XRD, XPS, XRF, CO-pulse chemisorption, N 2 -physisorption, Raman, TGA and TPR. The LDH-based catalyst showed superior activity to all other catalysts with conversions above 60% at only 400 °C. Additionally, it showed a stable activity over 70 h time on stream (TOS) without any deactivation. The superior activity and stability of the LDH-based catalyst was attributed to a homogeneous distribution of the Ni particles within an alumina-phase, inherited from the LDH precursor. This results in small Ni-particles with strong interactions with the alumina support, yielding a combination of very high activity, high stability of the particles and prevention of sintering.