The effects of manganese and potassium on the structural and morphological properties, phase compositions and CO adsorption behavior of the CNT-confined FeN catalyst were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fe-57 Mossbauer effect spectroscopy (MES) and CO temperature-programmed desorption (TPD). The results suggested that the presence of manganese helps retain nitrogen in cubic FeCxN1-x and facilitates CO adsorption. The selectivity to (C2C4=)-C-= light olefins is enhanced over Mn(1.0 wt%)/FeN/CNT although the activity decreases within the loading range of 0.5-2.0 wt% for Mn. Although further promotion with K could improve the activity slightly, the selectivity to light olefins decreases. At the same time, the addition of potassium enhanced the water gas shift activity and shifted the selectivity to heavy hydrocarbons (C5+), similar to the conventional reduced iron catalysts. (C) 2011 Elsevier B. V. All rights reserved.