A Gradient Nitrogen Doping Along Radial Direction of Carbon Nanotubes to Promote CO₂ Electroreduction

Abstract Developing metal‐free carbon catalysts with designable high nitrogen (N) content yet well‐organized N distribution within carbon at nanoscale is still one of the paramount challenges for electrochemical CO 2 conversion. Herein, a gradient N doping enabled by the energetic microwave irradiation is realized along the radial direction of carbon nanotubes (CNTs), with an ultrahigh surface N content of 30.5 at%, beyond the upper limit of the tradition pyrolysis method. The unique time‐domain features of microwave heating presented as the sub‐minute residence time for precursors and relatively mild surface temperature on CNTs, contributing to the maximum reservation of the surface N species. The catalyst exhibits a prominent performance with great activity and selectivity for electrochemical CO 2 ‐to‐CO conversion. Theoretical calculation confirmed the catalyst with high N‐doping level can promote the adsorption of CO 2 molecule, with a low adsorption energy of −3.35 eV. This work provides a novel prototype to construct the distribution‐controlled and space‐intensive active sites over functional gradient metal‐free carbon materials.