Pyridine-Grafted Nitrogen-Doped Carbon Nanotubes Efficiently Electrochemical Reduce C <sub>2</sub> to CO <sub>2</sub> at High Current Densities Over a Wide Electrochemical Window

Abstract

Nitrogen-doped carbon nanomaterials for electrochemical reduction of CO2 (CO2 ER) to CO have been extensively investigated, evaluated, and applied recently. Nevertheless, their weak adsorption capacity for CO2usually results in a rapidly decayed CO faradaic efficiencies (FECO) in the course of pursuing a commercial CO current density (j CO ) by increasing the overpotential. Herein, we axially graft pyridine molecules on nitrogen-doped carbon nanotubes to construct a metal-free composite electrocatalyst (Py-N 4 CNT-800) with enhanced CO2 affinity for CO2 ER to efficiently generate CO. Py-N4CNT-800 exhibits a prominent FECO of 96% at -0.99 V (vs. RHE) with a desirable jCO of 18.4 mA cm-2, and FECO can even be maintained above 90% in a wide electrochemical potential window (-0.79 to -1.19 V). In-situ infrared spectra unambiguously indicate that grafted axial pyridine molecules can facilitate the CO2 adsorption and suppress the occurrence of competitive hydrogen evolution reaction (HER). Notably, Py-N4CNT-800 delivers a promising jCO of 217 mA cm-2 at -0.9 V in flow cell, showing a bright prospect of functionstrengthened carbon nanomaterial for industrial applications.