High Selectivity in CO₂ Reduction to CO Using Metal-Decorated C₃N₄ Nanotubes

An important aspect of the CO₂ reduction reaction (CO2RR) is to inhibit the H₂ evolution reaction (HER) at the electrodes and to increase the formation of other valuable carbon products. In principle, a higher CO product selectivity allows for a higher amount of C₂₊ products in the CO2RR. Here, we report a material, the metal-decorated C₃N₄ nanotubes (M_n/CNNTs, n = 1 and 4), which exhibits high CO selectivity and low HER probabilities. Our DFT calculations indicate that this catalyst system strongly activates the CO₂ molecule through a unique adsorption site on the surface, which then undergoes the COOH intermediate transformation to CO. The results show that the single Fe or Cu atom combined with the armchair-type CNNTs shows the best CO selectivity with low CO2RR overpotentials (<0.4 V), signifying an opportunity for efficient and economical CO₂ conversion for future applications.