Electrochemical Oxygen Reduction Reaction in Alkaline Solution at a Low Overpotential on (220)-Textured Ag Surface

The oxygen reduction reaction (ORR) on a textured silver surface is investigated through computational modeling and experimental measurement. The reaction paths in three possible mechanisms of ORR on pure silver surfaces are analyzed by the transition-state searching method, and the Ag(220) surfaces exhibit an activation energy barrier of the O2 protonation reaction of 0.504 eV, which is the lowest activation energy barrier among the flat and stepped silver facets. Furthermore, the theoretical calculations show that the ORR overpotential of Ag(220) surfaces is 0.457 V, which is comparable to the overpotential of the Pt(111) catalyst, 0.441 V, indicating that the stepped Ag(220) facet is a high ORR active site on the textured silver surface. The ORR polarization curves of the textured silver surface are measured by the rotating disk electrode method and the experimental ORR activity trend is (220) facet > (111) facet > (200) facet for the textured silver surface. Both experimental and calculation results indicated that the stepped Ag(220) facet is one of high ORR activity origin for pure Ag materials with desirable morphologies. This new insight provides a fundamental understanding of the ORR reaction mechanism of monometallic Ag and the design of advanced catalytic materials based on pure Ag.