Carbon nanotubes with rich pyridinic nitrogen for gas phase CO2 electroreduction

Nitrogen doped carbon nanotubes (NCNTs) with high concentration of pyridinic N sites (62.3% of all nitrogen) were prepared by pyrolysis of phenathroline heterocycle precursor, and they can reduce CO2 to CO with high selectivity and stability. Faradaic efficiency of CO maintained >94.5% between −0.6 to −0.9 V vs the reversible hydrogen electrode (RHE), and the CO current density was as high as 20.2 mA cm−2. Moreover, during 40 h electrolysis at −0.8 V, Faradic efficiency for CO was stable at 95%. The high performance came from rich concentrations of pyridine N sites in NCNTs, serving as the active sites for catalysis. Furthermore, gas phase CO2 electrolysis showed nearly 100% Faradic efficiency for CO, suggesting that the NCNT can maximize the CO2 reduction efficiency and hydrogen evolution was suppressed completely.