Figure portrays the electrochemical free energy plot, highlighting the spontaneous and downhill nature of reactions at U = 0 V wherein all reaction steps in the plot exhibit negative ΔG values, say, ΔG < 0 V, affirming their thermodynamic favorability. The electrochemical free energy of all the reaction stages in the discharging reaction decreases until the electrode potential turns out to be 0.124 V. As a result, the studied RuO2 (211) surface has a discharge overpotential of 1.30 V (dis). Moreover, further increase in the electrode potential render the electron transfer reaction during the discharge to be thermodynamically uphill. This suggests that the last step the electron transfer reaction comprising MgCO3 with CO and MgCO3 with MgO and C adsorption is critical in regulating the discharge rate. Since the electrochemical free energy of each step in the reaction process decreased at a potential of 2.773 V, an overpotential of 1.35 V now exists during charging. The rate-controlling step during the charging process involves the decomposition of MgCO3 along with MgO and C accompanied with electron transfer. Total overpotential ηtotal is commonly employed to evaluate catalytic activity in the field of bifunctional catalysis for CO2RR/CO2ER, with a smaller value suggesting a greater degree of activity. The calculated total overpotential for overall electrochemical reaction process of non-aqueous Mg-CO2 battery using RuO2 (211) catalyst is 2.65 V. presents the discharge and charge overpotentials obtained from computational simulations of Li-CO2 batteries. The previous studies on Mg-CO2 batteries include only adsorption strength calculations as a descriptor to understand the reaction mechanism during the charging/discharging process. Nevertheless, in this study, we proposed the various possible reaction pathways during the reaction of CO2 cathode with Mg anode and moreover, for the first time, comprehensively investigated the entire electrochemical reaction mechanism during the CO2RR/CO2ER. We compared the results of this study to that of Li-CO2 batteries (see Figure ) because computational and experimental studies on non-aqueous Mg-CO2 is very scarce. While the calculated Mg-CO2 discharge-charge overpotential using RuO2 (211) is lower than that of α-Mo2C (001), β-Mo2C (001), it is comparable to that of Ti2C and Zr2C for Li-CO2 batteries respectively.