Curvature Effect of Pyridinic N-Modified Carbon Atom Sites for Electrocatalyzing CO₂ Conversion to CO

Carbon material is considered a promising electrocatalyst for the CO₂ reduction reaction (CO₂RR); especially, N-doped carbon material shows high CO Faradic efficiency (FE_CO) when using pyridinic N species as the active site. However, in the past decade, more efforts were focused on the preparation of various carbon nanostructures containing abundant pyridinic N species and few researchers studied the electronic structure modulation of the pyridinic N site. The curvature of the carbon substrate is an easily controllable parameter for modulating the local electronic environment of catalytic sites. In this research, carbon nanotubes (CNTs) with different diameters are applied to modulate the electronic environment of pyridinic N by the curvature effect. The pyridinic N sites doped on CNTs with the average curvature of 0.04 show almost 100% FE_CO at the current density of 3 mA cm^-2 at -0.6 V vs RHE and 91% FE_CO retention after 12 h test, which is superior to most of the carbon-based electrocatalysts. As demonstrated by density functional theory simulation, the pyridinic N site forms a strong local electric field around the nearby C active site and protrudes out of the curved CNT surface like a tip, which remarkably enriches the protons around the adsorbed CO₂ molecule.