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.