What Makes the Photocatalytic CO2 Reduction on N‑Doped Ta2O5 Efficient: Insights from Nonadiabatic Molecular Dynamics

Recent experimental studies demonstrated that photocatalytic CO2 reduction by Ru catalysts assembled on N-doped Ta2O5 surface is strongly dependent on the nature of the anchor group with which the Ru complexes are attached to the substrate. We report a comprehensive atomistic analysis of electron transfer dynamics in electroneutral Ru­(di-X-bpy) (CO)2Cl2 complexes with X = COOH and PO3H2 attached to the N–Ta2O5 substrate. Nonadiabatic molecular dynamics simulations indicate that the electron transfer is faster in complexes with COOH anchors than in complexes with PO3H2 groups, due to larger nonadiabatic coupling. Quantum coherence counteracts this effect, however, to a small extent. The COOH anchor promotes the transfer with significantly higher frequency modes than PO3H2, due to both lighter atoms (C vs P) and stronger bonds (double vs single). The acceptor state delocalizes onto COOH, but not PO3H2, further favoring electron transfer in the COOH system. At the same time, the COOH anchor is prone to decomposition, in contrast to PO3H2, making the former show smaller turnover numbers in some cases. These theoretical predictions are consistent with recent experimental results, legitimating the proposed mechanism of the electron transfer. We emphasize the role of anchor stability, nonadiabatic coupling, and quantum coherence in determining the overall efficiency of artificial photocatalytic systems.

近期实验研究表明，组装于氮掺杂五氧化二钽（N-doped Ta₂O₅）表面的钌催化剂用于光催化二氧化碳还原反应时，其催化性能强烈依赖于钌配合物与基底结合所用锚定基团的属性。本研究对锚定在N-Ta₂O₅基底上、X分别为羧基（COOH）和膦酸基（PO₃H₂）的电中性Ru(二-X-联吡啶)(CO)₂Cl₂配合物的电子转移动力学开展了全面的原子级分析。非绝热分子动力学（nonadiabatic molecular dynamics）模拟结果显示，由于非绝热耦合（nonadiabatic coupling）强度更高，带有羧基锚定基团的配合物的电子转移速率快于带有膦酸基锚定基团的配合物。然而，量子相干性（quantum coherence）会在一定程度上抵消这一效应。相较于膦酸基锚定基团，羧基锚定基团可通过更高频的振动模式促进电子转移，这源于其组成原子更轻（碳相较于磷）且化学键更强（双键相较于单键）。电子受体态会离域至羧基锚定基团，而非膦酸基锚定基团，这进一步提升了羧基体系的电子转移效率。与此同时，与膦酸基锚定基团相比，羧基锚定基团更易发生分解，这使得前者在部分场景下表现出更低的转化数（turnover number）。上述理论预测与近期实验结果相符，验证了所提出的电子转移机制的合理性。本研究强调了锚定基团稳定性、非绝热耦合以及量子相干性在决定人工光催化系统整体效率中的关键作用。