Ni nanoparticles inlaid in amorphous silicon nitride-derived nickel phyllosilicate: A highly stable and active catalyst for ammonia decomposition

The catalytic production of hydrogen (H₂) through the decomposition of ammonia (NH₃) using non-noble metal catalysts with small nanoparticles and high electronegativity at elevated loadings is considered a promising approach for efficient on-site H₂ production. However, excessive loading may undermine the interactions between the metal and the support, resulting in sintering and deactivation of the active components in catalysts at high temperatures. Herein, a layered nickel (Ni) phyllosilicate with varying Ni content was successfully synthesized using amorphous silicon nitride (Si₃N₄) as the silica source through a straightforward deposition–precipitation method. The characterization of Si₃N₄-derived Ni phyllosilicate indicates that it is more thermally stable than fumed SiO₂-derived Ni phyllosilicate when used as a catalyst precursor. Upon 700 °C reduction of Si₃N₄-derived Ni phyllosilicate containing 20.0 wt% Ni, small-sized (4.2 nm) and highly dispersion Ni nanoparticles were formed and embedded within the unreduced Ni Phyllosilicate matrix (NiPS-Red700). More importantly, the NiPS-Red700 is presented for efficient catalytic activity and stability for NH₃ decomposition at 700 °C with a gas hourly space velocity (GHSV) of 60,000 mL/g_cat/h, being much superior to Ni/SiO₂ catalysts prepared from the same synthesis method. The exceptional catalytic performance of NiPS-Red700 arises from the synergy of highly dispersed and electron-rich Ni nanoparticles, which facilitate the dissociation of the N–H bond and promote the combination of surface N* for N₂ associative desorption, ultimately enhancing the decomposition of NH₃.