NiCe@SiO2 core-shell-structured catalyst for an enhanced thermal stability for dry reforming of CH4 with CO2

Abstract

Dry reforming of methane with CO<inf>2</inf> (DRM) is an environmentally beneficial route to convert two major greenhouse gases into synthesis gas (syngas), contributing to an environmentally sustainable carbon cycle, which are generally suffered from significant catalyst deactivations through coke depositions and aggregations of active metal nanoparticles. To solve those intrinsic deactivation phenomena during the harsh DRM reaction conditions, a simple encapsulation strategy of typical Ni-CeO<inf>2</inf> core-side nanoparticles within inert silica shells at an optimal Ni/Ce ratio is proposed and it is found to be effective in preventing those aggregations of active metal nanoparticles with insignificant coke depositions. The stably preserved crystallite sizes of Ni nanoparticles even after a high-temperature DRM reaction, and oxygen vacant sites formed on the CeO<inf>2</inf> metal oxide promoter were responsible for an enhanced catalytic activity and stability by mitigating strong metal–support interactions with silica shells as well as by increasing CO<inf>2</inf> activation activity on the electron-rich Ni-CeO<inf>2</inf> interfaces as supported by DFT calculation results. The CeO<inf>2</inf>-promoted NiCe@SiO₂ catalyst at an optimal Ce/Ni molar ratio of 0.5 – 1.0 exhibited an improved DRM reaction activity and long-term stability, which were attributed to the highly dispersed active metallic Ni nanoparticles decorated with the CeO<inf>2</inf> metal oxides by enhancing CH<inf>4</inf> decomposition as well as successive CO<inf>2</inf> dissociation with the help of SiO<inf>2</inf> protective overlayers through effective suppression of coke formation and metal aggregation.