DFT study of and relevant to oxygen reduction with the presence of molten carbonate in solid oxide fuel cells

Using DFT methods, we have studied CO 4 2 - and CO 5 2 - relevant to oxygen reduction at the presence of molten carbonate in the cathode of fuel cells. The binding energy of CO2 to O 2 2 - is calculated to be 143 kcal mol−1, showing that peroxide plays an important role in the reduction of CO2 in MCFCs. The formation of CO 5 2 - from CO 3 2 - and O2 is exothermic, with an energy change of −24.3 kcal mol−1, which is comparable to the adsorption energy of oxygen on the defect sites of the LSM cathode of SOFCs. For 2 CO 3 2 - + O 2 ⇋ 2 CO 4 2 - , the equilibrium constant at 873 K is estimated to be 1.1 and CO 4 2 - is thermodynamically favored. The formation of CO 4 2 - and CO 5 2 - has significantly decreased the reduction potential of oxygen and will promote the ORR process in SOFCs.