Sandwiched SiO2@Ni@ZrO2 as a coke resistant nanocatalyst for dry reforming of methane

Abstract Design active and coke resistant Ni based catalysts is critical for implementation of dry reforming of methane technology. In this work, coke resistant SiO 2 @Ni@ZrO 2 catalyst has been successfully prepared through precipitation of nickel nitrate with ammonia onto silica spheres, followed by coating with porous ZrO 2 shell. Through thermal treatment in air and hydrogen, nickel nanoparticles with size of 6 nm were sandwiched between silica core and zirconia shell. The ZrO 2 coated Ni catalyst exhibited a high activity of ˜13.0 mol CH 4 per gram of Ni per hour for methane dry reforming at 700 °C, which is more than 6 times higher than that of SiO 2 @Ni catalyst under the same reaction condition. The SiO 2 @Ni@ZrO 2 catalyst is also coke resistant as no carbon formation was observed for methane dry reforming at 700 °C for 20 h. As a comparison, carbon nanotubes formed over SiO 2 @Ni catalyst during dry reforming reaction with a coking rate of 0.019 g of carbon formed per gram of catalyst per hour. Operando XANES/EXAFS study of SiO 2 @Ni@ZrO 2 catalyst confirmed metallic Ni phase during methane dry reforming from 400 to 800 °C. Theoretical calculations suggests that ZrO 2 stabilized Ni clusters lowers the highest dissociation energy barrier of CH 4 and CO 2 by 1.37 and 2.56 eV comparing to bulk Ni, increasing dry reforming activity on SiO 2 @Ni@ZrO 2 catalyst. Furthermore, the higher binding energy of CO 2 over CH 4 on SiO 2 @Ni@ZrO 2 leads to enrichment of CO 2 on catalyst surface, which mitigates coke formation.