Proton-coupled electron transfer (PCET) reactions on semiconducting metal oxide surfaces often involve charged defects in the form of electron or hole polarons. Herein, vibronically nonadiabatic PCET theory is used to model rate constants for the PCET reaction between a reduced anatase TiO₂(101) surface and 4-MeO-TEMPO, where electron polarons on the TiO₂ surface directly participate in the PCET reaction. This modeling strategy treats the transferring proton as well as all electrons quantum mechanically and includes the effects of excited vibronic states. The rate constant expression depends on the reorganization energy, as well as the reaction free energies and vibronic couplings for different pairs of vibronic states, and accounts for proton donor–acceptor motion. Hybrid functional periodic density functional theory (DFT) is used to calculate the parameters in the rate constant expression, and a Hubbard α-based constrained DFT approach is used to enforce charge constraints consistent with the two electronically diabatic states for the PCET reaction. This modeling strategy is applied to compute the PCET rate constants and kinetic isotope effects for reactions involving five-coordinate and six-coordinate Ti³⁺ defects on the TiO₂(101) surface, showing that excited vibronic states contribute significantly to the rate constant for both defects, especially for deuterium. This study highlights the importance of hydrogen tunneling and excited vibronic states in interfacial PCET reactions. Such modeling strategies can be used to further understand and tailor the reactivity of metal oxide surfaces for energy conversion.

中文翻译：

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通过金属氧化物表面上的局域陷阱态进行界面质子耦合电子转移

半导体金属氧化物表面上的质子耦合电子转移（PCET）反应通常涉及电子或空穴极化子形式的带电缺陷。在此，使用振动非绝热PCET理论来模拟还原锐钛矿TiO ₂ (101)表面和4-MeO-TEMPO之间的PCET反应的速率常数，其中TiO ₂表面上的电子极化子直接参与PCET反应。该建模策略以量子力学的方式处理传输的质子以及所有电子，并包括激发电子振动态的影响。速率常数表达式取决于重组能、反应自由能和不同振动电子态对的振动耦合，并解释质子供体-受体运动。混合泛函周期密度泛函理论 (DFT) 用于计算速率常数表达式中的参数，并使用基于 Hubbard α 的约束 DFT 方法来强制与 PCET 反应的两个电子非绝热态一致的电荷约束。该建模策略用于计算TiO _{2 (101) 表面上涉及五配位和六配位 Ti} ³⁺缺陷的反应的 PCET 速率常数和动力学同位素效应，表明激发的振动电子态对速率常数有显着贡献。这两种缺陷，尤其是氘。这项研究强调了氢隧道效应和激发电子振动态在界面 PCET 反应中的重要性。这种建模策略可用于进一步了解和定制金属氧化物表面的能量转换反应性。