Understanding the importance of N-doping for CNT-supported Ni catalysts for CO2 methanation

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 X-CO2 of 81.2% with S-CH4 = 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.(C)022 Elsevier Ltd. All rights reserved.