Mechanistic Studies of Oxygen Reduction by Hydrogen on PdAg(110)

Abstract

First principles electronic structure calculations based on periodic, self-consistent density functional theory (DFT-GGA) were utilized to study the mechanism of the vapor phase reaction between hydrogen and oxygen on the PdAg(110) alloy surface. The hydrogen–oxygen reaction is an important reaction in the direct synthesis of hydrogen peroxide (H2O2) and at the cathode in proton exchange membrane fuel cells (PEMFCs). Our results demonstrate that the minimum energy path involves the initial formation of a peroxyl (OOH) intermediate followed by O–O bond scission, consistent with the minimum energy path shown on the (111) facet of monometallic Pd and Ag surfaces. The lower activation energy barrier for O–O bond scission in OOH versus hydrogenation of OOH to form HOOH, and the low barrier for HOOH decomposition, suggest that PdAg(110) may not be an effective catalyst for the direct synthesis of H2O2. The detailed thermochemistry and activation energy barriers of important elementary steps and intermediates in...