Chemical route to prepare nickel supported on intermetallic Ti6Si7Ni16 nanoparticles catalyzing CO methanation.

Abstract

In this study, ternary intermetallic nickel silicide, Ti6Si7Ni16, nanoparticles with a high surface area of 37.5 m2 g-1 were chemically prepared from SiO2-impregnated oxide precursors, which were reduced at as low as 600 °C by a CaH2 reducing agent in molten LiCl, resulting in the formation of single-phase Ti6Si7Ni16 with a nanosized morphology. The intermetallic Ti6Si7Ni16 phase in the nanoparticles was stabilized in air by surface passive oxide layers of TiOx-SiOy, which facilitated the handling of the nanoparticles. Considering our previous successful work of preparing single-phase LaNi2Si2 (39.3 m2 g-1) and YNi2Si2 (27.0 m2 g-1) nanoparticles in a similar manner, the proposed chemical method showed to be a versatile approach in preparing ternary silicide nanoparticles. In this study, we applied the obtained Ti6Si7Ni16 nanoparticles as catalyst supports in CO methanation. The supported nickel catalyst showed an activation energy of 56 kJ mol-1, which is half as low as that of common TiO2-supported nickel catalysts. Also, Ni/Ti6Si7Ni16 provided the lower activation energy more than any previous Ni-based catalyst. Since the measured work function of Ti6Si7Ni16 (4.5 eV) was lower than that of nickel (5.15 eV), it was suggested that the Ti6Si7Ni16 support can accelerate the rate-determining step of C-O bond dissociation in CO methanation due to its good electron donation capacity.