Unraveling the Molecular Mechanism of H2O2 Production on Au–Pd Nanoalloy Surfaces

Oxygen reduction reaction (ORR) can proceed along two distinct pathways: the 4-electron pathway and the 2-electron pathway. The 4-electron pathway holds significant value in fuel cell technology, whereas the 2-electron pathway plays a crucial role in the industrial production of H2O2. Accurate prediction of the catalytic selectivity in the ORR stands as a pivotal factor in designing effective catalyst materials. It has been experimentally demonstrated that Au–Pd nanoalloy exhibit a high selectivity toward electrocatalytic H2O2 production. However, based on the widely employed computational hydrogen electrode method, the production of H2O on the surface of Au–Pd nanoalloy is more thermodynamically favorable, which shows a discrepancy with experimental results. In this work, we systematically investigate the influence of aqueous environment as well as electrode potential toward the ORR employing state-of-the-art ab initio molecular dynamics and metadynamics simulations. Our work reveals that the water molecules above the Au–Pd nanoalloy surface can alter the adsorption behavior of O2 and weaken the interaction between metal atom in the catalyst and oxygen atom in O2, therefore contributing to a high selectivity of Au–Pd nanoalloy toward H2O2 production. With a more negative electrode potential, the stability of H2O2 will decrease, and the corresponding selectivity will be lowered. These discoveries provide a dynamic perspective elucidating efficient H2O2 production on Au–Pd nanoalloy surfaces. Furthermore, they underscore the paramount significance of both the aqueous environment and electrode potential in shaping the ORR process.