A decomposition mechanism of H2O2 by triphenylphosphine oxide (TPPO) is presented. TPPO is often incorporated in proton-exchange membrane electrolytes as a moiety to inhibit the H2O2-induced degradation of the membranes. However, it has not been revealed how TPPO decreases the concentration of free H2O2 in the membranes. Following the experimental X-ray structures, the TPPO dimer capturing two H2O2 molecules was used as the calculation model. The vibrational spectrum calculations for various hydration numbers show that this model correctly reproduces the spectral peaks of TPPO capturing H2O2. On the basis of this model, the H2O2 decomposition mechanism by the TPPO dimer was searched. It was consequently found that this reaction proceeds through three steps: (1) Hydrogen transfer from H2O2 to the P=O bond of TPPO, (2) Hydrogen transfer from the -OOH group to the -OH group, and (3) O-O bond formation between O2 groups. The calculated vibrational spectra for the reactants and intermediates indicated that the first and second steps are activated by vibrational excitations. Moreover, the third step giving low barrier heights is considered to proceed through two reaction paths: directly producing the O2 molecule or going through an HOOOH intermediate. Interestingly, this reaction mechanism was found to use the violation of the octet rule for the P=O double bond, resulting in the strong H2O2 binding of TPPO.

中文翻译：

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三苯基膦氧化物分解H2O2的机理。

提出了三苯膦氧化物（TPPO）对H2O2的分解机理。TPPO通常作为质子交换膜电解质的一部分，以抑制H2O2引起的膜降解。然而，尚未揭示TPPO如何降低膜中游离H 2 O 2的浓度。根据实验的X射线结构，将捕获两个H2O2分子的TPPO二聚体用作计算模型。各种水合数的振动光谱计算表明，该模型正确地再现了TPPO捕获H2O2的光谱峰。在此模型的基础上，研究了TPPO二聚体分解H2O2的机理。因此发现该反应通过三个步骤进行：（1）氢从H2O2转移至TPPO的P = O键，（2）从-OOH基团到-OH基团的氢转移，和（3）在O 2基团之间形成OO键。计算出的反应物和中间体的振动光谱表明，第一步和第二步是通过振动激发来激活的。而且，第三步给出低的势垒高度被认为是通过两个反应路径进行的：直接产生O2分子或通过HOOOH中间体。有趣的是，发现该反应机制对P = O双键使用了违反八位位组规则的结果，从而导致TPPO与H2O2的强结合。第三步给出较低的势垒高度，它被认为是通过两个反应路径进行的：直接生成O2分子或通过HOOOH中间体。有趣的是，发现该反应机制对P = O双键使用了违反八位位组规则的结果，从而导致TPPO与H2O2的强结合。第三步给出较低的势垒高度，它被认为是通过两个反应路径进行的：直接生成O2分子或通过HOOOH中间体。有趣的是，发现该反应机制对P = O双键使用了违反八位位组规则的结果，从而导致TPPO与H2O2的强结合。