Thermodynamic Insights into Electrochemical CO Reduction to Methanol and Ethanol over Fe- and Cu-Decorated g-C3N4 Nanotubes: A DFT Study

Single-atom catalysts based on one-dimensional graphitic carbon nitride nanotubes (CNNTs)—tubular frameworks derived from g-C3N4—have shown promising activity for the electrochemical conversion of CO2 to CO. To elucidate the mechanisms governing the subsequent reduction of CO, density functional theory calculations were performed to examine the CO reduction reaction (CORR) on Fe- and Cu-decorated CNNTs (Fe/aN-6 and Cu/aN-6). Thermodynamic analyses indicate distinct metal-dependent reaction pathways: Fe/aN-6 exhibits a C1 pathway toward methanol with a limiting potential of –0.76 V and an overpotential of 0.87 V. In contrast, Cu/aN-6 exhibits C1 and C2 pathways, with limiting potentials of –0.96 and –0.98 V and overpotentials of 1.07 and 1.17 V for methanol and ethanol, respectively. These findings highlight the influence of the transition-metal center on CORR products and provide theoretical guidance for tailoring carbon-nitride-based electrocatalysts.