Staszak-Jirkovský Jakub, Ahlberg Elisabet, Panas Itai, Schiffrin David J
Chemistry Department, University of Liverpool, L69 7ZD, UK.
Department of Chemistry and Molecular Biology, University of Gothenburg, SE-412 96, Gothenburg, Sweden.
Faraday Discuss. 2016 Jul 4;188:257-78. doi: 10.1039/c5fd00233h.
The oxygen reduction reaction is of major importance in energy conversion and storage. Controlling electrocatalytic activity and its selectivity remains a challenge of modern electrochemistry. Here, first principles calculations and analysis of experimental data unravel the mechanism of this reaction on Au-Pd nanoalloys in acid media. A mechanistic model is proposed from comparison of the electrocatalysis of oxygen and hydrogen peroxide reduction on different Au-Pd ensembles. A H2O production channel on contiguous Pd sites proceeding through intermediates different from H2O2 and OOH(σ) adsorbate is identified as the bifurcation point for the two reaction pathway alternatives to yield either H2O or H2O2. H2O2 is a leaving group, albeit reduction of H2O2 to H2O can occur by electrocatalytic HO-OH dissociation that is affected by the presence of adsorbed OOH(σ). Similarities and differences between electrochemical and direct synthesis from H2 + O2 reaction on Au-Pd nanoalloys are discussed.
氧还原反应在能量转换和存储中至关重要。控制电催化活性及其选择性仍然是现代电化学面临的一项挑战。在此，通过第一性原理计算和实验数据分析揭示了该反应在酸性介质中Au-Pd纳米合金上的反应机理。通过比较不同Au-Pd组合上氧还原和过氧化氢还原的电催化过程，提出了一个机理模型。在相邻的Pd位点上，通过不同于H2O2和OOH(σ)吸附物的中间体生成H2O的通道被确定为两条反应途径产生H2O或H2O2的分支点。H2O2是一个离去基团，尽管H2O2通过受吸附的OOH(σ)存在影响的电催化HO-OH解离可还原为H2O。文中还讨论了在Au-Pd纳米合金上电化学合成与H2 + O2直接合成之间的异同。
