Atomically\nDispersed Iron–Nitrogen Sites on\nHierarchically Mesoporous Carbon Nanotube and Graphene Nanoribbon\nNetworks for CO₂ Reduction

Abstract

Atomically dispersed\nmetal and nitrogen co-doped carbon (M-N/C)\ncatalysts hold great promise for electrochemical CO₂ conversion.\nHowever, there is a lack of cost-effective synthesis approaches to\nmeet the goal of economic mass production of single-atom M-N/C with\ndesirable carbon support architecture for efficient CO₂ reduction. Herein, we report facile transformation of commercial\ncarbon nanotube (CNT) into isolated Fe–N₄ sites\nanchored on carbon nanotube and graphene nanoribbon (GNR) networks\n(Fe-N/CNT@GNR). The oxidization-induced partial unzipping of CNT results\nin the generation of GNR nanolayers attached to the remaining fibrous\nCNT frameworks, which reticulates a hierarchically mesoporous complex\nand thus enables a high electrochemical active surface area and smooth\nmass transport. The Fe residues originating from CNT growth seeds\nserve as Fe sources to form isolated Fe–N₄ moieties\nlocated at the CNT and GNR basal plane and edges with high intrinsic\ncapability of activating CO₂ and suppressing hydrogen evolution.\nThe Fe-N/CNT@GNR delivers a stable CO Faradaic efficiency of 96% with\na partial current density of 22.6 mA cm^–2 at a low\noverpotential of 650 mV, making it one of the most active M-N/C catalysts\nreported. This work presents an effective strategy to fabricate advanced\natomistic catalysts and highlights the key roles of support architecture\nin single-atom electrocatalysis.