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.

中文翻译：

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揭示 Au-Pd 纳米合金表面产生 H2O2 的分子机制

氧还原反应 (ORR) 可以沿着两种不同的途径进行：4 电子途径和 2 电子途径。 4电子途径在燃料电池技术中具有重要价值，而2电子途径在H ₂ O ₂的工业生产中起着至关重要的作用。准确预测 ORR 中的催化选择性是设计有效催化剂材料的关键因素。实验证明Au-Pd纳米合金对电催化H ₂ O ₂生产表现出高选择性。然而，基于广泛采用的计算氢电极方法，Au-Pd纳米合金表面H ₂ O的产生在热力学上更为有利，这与实验结果存在差异。在这项工作中，我们采用最先进的从头算分子动力学和元动力学模拟，系统地研究了水环境以及电极电位对 ORR 的影响。我们的工作表明，Au-Pd纳米合金表面上方的水分子可以改变O ₂的吸附行为，削弱催化剂中金属原子与O ₂中氧原子之间的相互作用，从而有助于Au-Pd纳米合金的高选择性朝向H ₂ O ₂生产。电极电位越负，H ₂ O ₂的稳定性就会降低，相应的选择性也会降低。这些发现为阐明Au-Pd 纳米合金表面上H ₂ O ₂的高效生产提供了动态视角。此外，他们强调了水环境和电极电位在形成 ORR 过程中的至关重要性。