Bifunctional carbon elimination mechanism of CeO2 nanorod@Ni3Co7Phy core shell catalyst for CO2 reforming of methane

Abstract

CO₂ capture and utilization via reforming of methane (DRM) is an efficient route to promote the achievement of the carbon neutralization goal. Whereas, the carbon deposition problem on cheap Ni-based catalysts slows down its industrial progress. Although Co doping to form NiCo bimetallic catalysts is effective to enhance the carbon resistance, the bifunctional carbon elimination mechanism has not been unveiled. Here, core shell structured CeO₂@Ni₇Co₃Phy catalyst with high sintering and carbon resistance has been designed, exhibiting the stable CH₄ and CO₂ conversion of 72 % and 78 % respectively at 973 K for 120 h. The outstanding performance is due to the formation of Ni₇Co₃ bimetal, enhanced metal support interaction, and the highest surface Ni⁰ concentration, increasing sintering resistance and boosting the DRM activity. In situ diffuse infrared Fourier transform spectroscopy analysis and density functional theory calculations further confirm the bifunctional carbon elimination mechanism that both the oxygen vacancies in CeO₂ and the electron deficient oxidative Co sites adsorb and activate CO₂, providing oxygen species to eliminate carbon. By comparison, either serious Ni sintering and carbon accumulation or oxidation of Co⁰ phase due to excessive CO₂ activation occurred for CeO₂@NiPhy and CeO₂@CoPhy catalyst respectively, leading to their worse DRM performance. The bifunctional carbon elimination mechanism illuminates the design of other carbon resistant catalysts.