Screening Transition Metals (Mn, Fe, Co, and Cu) Promoted Ni-Based CO2 Methanation Bimetal Catalysts with Advanced Low-Temperature Activities

Abstract

The Ni monometallic catalyst usually exhibits poor CO₂ methanation activity, although its low cost is beneficial for conducting large-scale application in industries. Herein, the transition metal (Mn, Fe, Co, and Cu)-doped Ni-based bimetallic catalysts loaded on mesoporous Ce₀.₈Zr₀.₂O₂ solid solution were prepared to address this challenge in CO₂ methanation. We found that the Co-doped catalysts exhibited much higher activity than the corresponding counterparts. Therefore, the relationship between the Co/Ni ratio and activity was further investigated to acquire the optimum ratio. The obtained catalysts were characterized by various measurements. The results demonstrated that doping the second transition metals could promote Ni dispersion and strengthen metal–support interaction. Resultantly, serious agglomeration of the metallic active sites was successfully inhibited. Besides, we also carried out the in situ diffuse reflectance infrared spectroscopy and online temperature-programmed surface reaction of CO₂ methanation to study the possible reaction intermediates and pathways over the Ni–Co bimetallic catalysts. A dynamic study was also conducted to further study the effect of the doped transition metals on the apparent activation energies. Besides, the present research also revealed that the Ni–Co synergistic effect significantly improved the low-temperature activity by regulating the reaction intermediates. As a result, the Ni–Co bimetallic catalysts supported by mesoporous Ce₀.₈Zr₀.₂O₂ solid solution were considered as a series of promising and efficient low-temperature CO₂ methanation catalysts.