(326c) Density Functional Theory Determination of Potential Dependent Anion Adsorption of Relevance to Cathode Performance of Microbial Fuel Cells and Microbial Electrolysis Cells

Anion adsorption affects electrocatalytic reaction rates by blocking active sites, altering adsorbed species stability, or modifying the electrostatic potential distribution at the interface. In this talk, a series of density functional theory (DFT) approaches to evaluating the electrode potential dependent adsorption free energy of anions are evaluated. Of specific interest are adsorbed anion effects on electrode kinetics at microbial fuel cell and microbial electrolysis cell cathodes where the oxygen reduction reaction (ORR) and the hydrogen evolution reaction (HER) occur. These cells operate in buffered solutions containing various anions. DFT is used to simulate the experimental voltammogram for anion adsorption, and the potential dependent anion coverages are used to explain experimental electrode kinetics of HER and ORR in the presence of acetate and phosphate solutions.. Acetate, dihydrogen and hydrogen phosphate effects are considered on Pt cathodes. Linear sweep voltammetry is used to evaluate HER and ORR kinetics in the presence of various anions. The importance of anion adsorption in the selection of ORR and HER catalysts for operation in neutral pH, buffered solutions will be discussed.