A theoretical study of CO adsorption on FeCo(100) and the effect of alloying

► Alloying Fe and Co changes in preferable metal for CO adsorption. ► CO preferentially adsorbs on the Co-site of the FeCo alloys rather than the Fe-site. ► FeCo(100) is more reactive than pure Fe or Co surface due to lower work function. ► d-band center of Co atoms in FeCo alloy moves closer to Fermi level. ► d-band center of Fe atoms in FeCo alloy moves away from the Fermi level.