Prediction of the dependence of the fuel cell oxygen reduction reactions on operating voltage from DFT calculations

To use density functional theory (DFT) to seek improved catalysts for the oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell, we developed a systematic way to handle the barriers of electron transfer reactions (e.g., H ⁺ + e- + O _ad → OH _ad) within the DFT framework. We report applications of this new method to determining the dependence for the barriers of various ORR reaction steps on the operating electrochemical potential for the Pt-catalyzed fuel cell. This method is used to estimate the optimum operating potential. In the Article, we show how to estimate the change in efficiency from changes in the reaction barriers. On the basis of our mechanism and calculated barriers, the optimum operating voltage for the ORR on Pt is found to be 0.68 V/NHE, which is close to the standard operating voltage of ∼0.8 V/NHE, validating this analysis.