Understanding the importance of N−doping for CNT-supported Ni catalysts for CO2 methanation
Liliana P. L. Gonçalves, Maria Meledina, Alexander Meledin, Dmitri Y. Petrovykh, Juliana P. S. Sousa, O.S.G.P. Soares, Yury V. Kolen’ko, M. Fernando R. Pereira
Abstract
The N−doping of carbon nanotubes (CNTs) is widely accepted as an effective way to enhance the catalytic performance of CNT-supported Ni catalysts for CO2 methanation. To demonstrate, in a direct systematic comparison, the importance of N−doping for producing high-performance CO2 methanation catalysts, we developed two catalysts composed of 15 wt% Ni on pristine (Ni/CNT) and N−doped CNT (Ni/CNT−N) and correlated their catalytic performance with their properties. Compared to Ni/CNT, Ni/CNT−N achieved a higher XCO2 of 81.2% with SCH4 = 99.2% at a lower temperature of 400 °C, exhibiting excellent stability over 48 h time-on-stream testing. Our comprehensive comparative study demonstrated that the N−doped CNT support featured a better distribution of the Ni sites that were strongly interacting with the support, even with atomically dispersed Ni being observed by HAADF-STEM. This higher dispersion, enabled by the anchoring sites provided by the N−doping, is one of the main reasons for the enhanced performance of Ni/CNT−N, because it increases the H2 uptake capacity.