Curvature of NCNTs induced selectivity of CO₂ electroreduction into CO

Nitrogen-doped carbon nanotubes (NCNTs) are usually selective and robust electrocatalysts for CO₂ reduction to CO in aqueous media. However, the electronic property of NCNTs is strongly dependent on their curvature, the change of curvature has a great impact on the electrocatalytic performance. Therefore, it is highly desirable to clarify the curvature effect of NCNTs for CO₂RR performance. Herein, we investigated the CO₂RR performances of NCNTs with different curvatures, which were obtained by doping N into CNTs under high temperatures. And low curvature of l-NCNT-1000 presented the highest CO FE (88.5%), which was much higher than that of the mid curvature of M-NCNT-1000 (71.1%) and the high curvature of S-NCNT-1000 (58%). According to density functional theory (DFT) calculations, the pyridine-N site was considered a catalytic active site for CO₂RR regardless of the low, mid or high curvature structure. Moreover, the low curvature surface of NCNTs had a relatively large binding energy with the HOCO* intermediate that is the principal intermediate for the CO₂RR, thereby enhancing the catalytic activity of CO₂ electroreduction to CO.