Functional Group Engineering of Single-Walled Carbon Nanotubes for Anchoring Copper Nanoparticles Toward Selective CO2 Electroreduction to C2 Products

Abstract

Electroreduction of carbon dioxide (CO₂) is a key strategy for achieving net-zero carbon emissions. Copper (Cu)-based electrocatalysts have shown promise for CO₂ conversion into valuable chemicals but are hindered by limited C₂₊ product selectivity due to competing hydrogen evolution and ineffective dimerization of adsorbed CO intermediate (^*CO). Here, a functional-group-directed strategy is reported to enhance selectivity using single-walled carbon nanotubes (SWCNTs) as supports. The catalytic performance of Cu nanoparticles is strongly influenced by the type and density of functional groups on the SWCNTs. Optimized Cu/amine-functionalized SWCNTs achieved a Faradaic efficiency of 66.2% and a partial current density of −270 mA cm⁻² for C₂ products within a flow cell, outperforming Cu/SWCNTs and Cu/cyano-functionalized SWCNTs. Density functional theory calculations revealed that the electron-donating amine groups can facilitate electron transfer from the graphite sheet to Cu atoms, thereby shifting the d-band center of Cu upward. This shift enhances ^*CO and its hydrogenation derivative adsorption and promotes water splitting, leading to an increased tendency for the generation of C₂ products. In situ infrared and Raman spectroscopy confirm the enhancement of key ^*CHO intermediate coverage, facilitating C─C coupling. This work provides a molecular framework for exploring interactions between functional groups and active metals in CO₂ electrolysis, offering insights for designing catalysts for a broad range of electrocatalytic processes.