Modulation Engineering of Graphitic/Pyrrolic Nitrogen Co-Doped Porous Carbon-Based Electrocatalysts with Abundant Active Sites for Efficient CO2 Reduction

Abstract

Developing metal-free catalysts is critical to addressing the issues of susceptibility to poisoning and deficient durability in the electrocatalysis of metal-based materials for CO₂ reduction reaction (CO₂RR). Herein, N-doped carbon nanoparticles (NCs) with a specific ratio of graphitic/pyrrolic N, high specific surface area, and abundant nanopores are synthesized by pyrolyzing a Cu and Zn co-coordinated polymer with bis(imino)-pyridine ligands. Results demonstrate that precise co-incorporation of Cu and Zn in the precursor effectively modulates the N doping species and ratios of NCs, as well as the pore structure, resulting in significantly distinct CO₂RR behaviors. The NCs synthesized by the precursor with the ratio of Zn and Cu ions (1 : 4), featuring graphitic-N and pyrrolic-N in the ratio of 2 : 1 and high specific surface area (896.8 m² g⁻¹), exhibit a low onset potential of −0.4 V_RHE, an exceptional CO Faradaic efficiency of 96.1 %, and a power density of 0.8 mW cm⁻² in a Zn−CO₂ battery. Theory calculations reveal that regulating the graphitic/pyrrolic N ratio can redistribute the localized atoms′ charge density, which enhances the adsorption of intermediate COOH* and mobilizes multiple active atomic sites favoring CO₂RR. The discovery in this work provides a new understanding for the design of advanced metal-free CO₂RR electrocatalysts.