Tuning catalytic performances of cobalt catalysts for clean hydrogen generation via variation of the type of carbon support and catalyst post-treatment temperature

摘要

Multi-walled carbon nanotubes, three types of activated carbons, single wall carbon nanotube and reduced graphene oxides were used to synthesize nano-sized Co catalysts for H_2 preparation via NH_3 decomposition. Catalyst samples were characterized by number of techniques such as N_2 physisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopes (XPS), Transmission electron microscopy (TEM), CO chemisorption, temperature-programmed reduction (H_2-TPR) and temperature-programmed desorption (N_2-TPD). The catalytic activities of the studied catalysts for H_2 production via NH_3 decomposition were measured in a fixed-bed micro-reactor. Co catalyst supported on multi-wall carbon nanotubes has shown the highest catalytic activity. The Co particles size was significantly affected by the variation of the post-treatment temperature. The Co particles size in the range of 4.7-64.8 nm can be effectively controlled by varying post-treatment temperature between 230 and 700 ℃. The maximum TOF of NH_3 decomposition was registered on cobalt catalyst post-treated at 600 ℃.