The effects of CO2 on physical and electrochemical properties of deep eutectic solvent (DES) containing Fe (II)/Fe(III) redox couple were studied. At 25 degrees C, the viscosity of the DES decreased from 690.4 cP to 620 cP (10.1% decrease), and the ohmic resistance reduced from 1867 Omega to 1409 Omega (24.5% decrease) with saturated CO2. The magnitude of the changes reduces with the increase of temperature. Moreover, the cyclic voltammetry curve shows that the addition of CO2 has no remarkable influence on the reaction kinetics of redox couple in DES. The results reported here imply that CO2 has positive effects on the physicochemical characteristics of DES, while further studies are needed for being used in a DES electrolyte flow battery. (C) 2018 Elsevier B.V. All rights reserved.