Atomically Dispersed Iron–Nitrogen Sites on Hierarchically Mesoporous Carbon Nanotube and Graphene Nanoribbon Networks for CO2 Reduction

Abstract

Atomically dispersed metal and nitrogen codoped carbon (M-N/C) catalysts hold great promise for electrochemical CO₂ conversion. However, there lack cost-effective synthesis approaches to meet the goal of economic mass production of single-atom M-N/C with desirable carbon support architecture for efficient CO₂ reduction. Herein, we report facile transforming commercial carbon nanotubes into isolated Fe−N₄ sites anchored on carbon nanotubes and graphene nanoribbons networks (Fe-N/[email protected]). The oxidization-induced partial unzipping of CNTs results in the generation of GNRs nanolayers attached to the remaining fibrous CNTs frameworks, which reticulates a hierarchically mesoporous complex and thus enables high electrochemical active surface area and smooth mass transport. The Fe residues originated from CNTs growth seeds serve as Fe sources to form isolated Fe−N₄ moieties located at the CNTs and GNRs basal plane and edges with high intrinsic capability of activating CO₂ and suppressing hydrogen evolution. The Fe-N/[email protected] delivers a stable CO Faradic efficiency of 96% with a partial current density of 22.6 mA cm⁻² at a low overpotential of 650 mV, making it one of the most active M-N/C catalysts reported. This work presents an effective strategy to fabricate advanced atomistic catalysts and highlights the key roles of support architecture in single-atom electrocatalysis.