CO2 conversion to synthesis gas via DRM on the durable Al2O3/Ni/Al2O3 sandwich catalyst with high activity and stability
CO2 conversion to synthesis gas with a CO/H2 molar ratio around 1 was realized by using the dry reforming of methane reaction (DRM) at 800 °C. The key problem was to design catalysts with both high activity and strong durability at such a high reaction temperature. This work developed a novel Al2O3/Ni/Al2O3 sandwiched catalyst prepared by coating Al2O3-supported Ni nanoparticles with a porous Al2O3 thin film by atomic layer deposition (ALD). The catalyst with 80 layers of Al2O3 thin films exhibited the highest activity. Both CO2 and CH4 conversions reached nearly 100% with absolute selectivities towards CO and H2. More importantly, this catalyst displayed excellent stability and could be used for more than 400 h in the DRM reaction at 800 °C without significant deactivation. Mechanism analysis revealed that the deactivation mainly resulted from the gathering of Ni nanoparticles at high temperature, corresponding to the decrease of Ni active sites. Moreover, a large-sized Ni active site could easily cause carbon deposition, which could further accelerate the catalyst deactivation. The Al2O3/Ni/Al2O3 sandwiched catalyst could effectively protect Ni nanoparticles from gathering owing to the double strong interactions between the Ni active sites and Al2O3 support.