Phyllosilicate-derived Ni catalysts with small nanoparticle size and strong metal-support interaction for efficient and robust decomposition of ammonia

Abstract

Ammonia decomposition is a structure-sensitive reaction, so the difference in structure of similar catalysts may have a great impact on the catalytic performance of ammonia decomposition reaction. However, it is not clear which structural properties can play a role in ammonia decomposition reaction and the degree of influence on catalytic performance. To explore this question, ammonia evaporation-hydrothermal (AEH), impregnation (IM), and evaporation-induced self-assembly (EISA) methods were used to synthesize Ni/SiO2 catalysts to obtain carbon-free hydrogen from catalyzing NH3 decomposition reaction. Among the three, the Ni/SiO2 catalyst synthesized via ammonia evaporation-hydrothermal method is the smallest in terms of Ni nanoparticles (∼3.0 nm) and the strongest Ni-SiO2 interaction. For ammonia decomposition, it is the highest in activity and thermal stability. The NH3 conversion at 650 °C and 30 000 mL gcat−1h−1 (GHSV) over Ni/SiO2-AEH was close to 90 % and remained stable in an evaluation period of 60 h.