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 (Mn/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.