Standard enthalpy of formation of NaxCoO2 system

► Sodium-cobalt oxides NaxCoO2 (x = 0.1, 0.2…0.9) have been synthesized and characterized. ► The heat of dissolutions of NaxCoO2, NaCl(s), CoCl3(s) and H2O (l) in aqueous HCl solution were measured. ► The standard molar enthalpies of formation (ΔfHm°298) of NaxCoO2 compounds are determined. ► The standard molar enthalpy of formation of NaxCoO2 compounds were compared with similar class of compounds.