Wu Siyi, Ma Jianzheng, Zhang Changwei, Prezhdo Oleg V, Zhao Jin, Gong Xin-Gao, Chu Weibin
Key Laboratory for Computational Physical Sciences (MOE), State Key Laboratory of Surface Physics, Institute of Computational Physical Sciences and Department of Physics, Fudan University, Shanghai 200433, China.
Department of Chemistry and Department of Physics & Astronomy, University of Southern California, Los Angeles, California 90089, United States.
J Am Chem Soc. 2025 Jun 18;147(24):21060-21067. doi: 10.1021/jacs.5c06155. Epub 2025 Jun 7.
The photocatalytic efficiency of a molecule/metal oxide interface critically depends on the dynamic competition between forward carrier transfer to the molecule and reverse transfer to the substrate. Using CHO/TiO as a prototypical system and employing nonadiabatic molecular dynamics simulations with hybrid density functional theory, we reveal the complete cascade of atomistic processes following photoexcitation. Our results demonstrate that accurately predicting carrier dynamics in photocatalysis requires a comprehensive understanding of the full photochemical sequence involves carrier trapping, post-trapping stabilization, and subsequent dissociation. In the trapping process, despite an unfavorable 0.55 eV HOMO-VBM offset under static conditions that would suggest minimal hole trapping, thermal fluctuations dynamically modulate adsorbate-substrate hybridization, enabling transient photogenerated hole capture. Critically, when trapped hole stabilization occurs via CHO radical formation, the reverse transfer time scale dramatically extends from sub-10 fs to sub-10 ps, a rise of 3 orders of magnitude. This radical state elevates the trap-state energy, suppressing reverse transfer and extending carrier lifetimes sufficiently to enable subsequent chemistry. The metastable radical further reduces the C-H dissociation barrier, driving spontaneous photodecomposition via proton-coupled charge transfer. Our findings reconcile long-standing theory-experiment discrepancies by demonstrating that a dual energy alignment framework in the molecule/metal oxide interface: initial charge capture requires pretrapping energy matching, while post-trapping stabilization via chemical intermediates creates an energetic asymmetry that effectively suppresses carrier dissipation. This mechanistic understanding of interfacial charge dynamics provides fundamental design principles for the rational development of high-efficiency photocatalytic systems.
分子/金属氧化物界面的光催化效率关键取决于正向载流子向分子转移与反向转移至底物之间的动态竞争。以CHO/TiO作为典型体系，并采用基于杂化密度泛函理论的非绝热分子动力学模拟，我们揭示了光激发后完整的原子过程级联。我们的结果表明，准确预测光催化中的载流子动力学需要全面理解整个光化学序列，该序列涉及载流子捕获、捕获后稳定化以及随后的解离。在捕获过程中，尽管在静态条件下存在不利的0.55 eV的最高占据分子轨道-价带顶偏移，这表明空穴捕获极少，但热涨落会动态调节吸附质-底物杂化，从而实现瞬时光生空穴捕获。至关重要的是，当通过CHO自由基形成实现捕获空穴的稳定化时，反向转移时间尺度从亚10飞秒急剧延长至亚10皮秒，增加了3个数量级。这种自由基态提高了陷阱态能量，抑制了反向转移并充分延长了载流子寿命，从而能够进行后续化学反应。亚稳态自由基进一步降低了C-H解离势垒，通过质子耦合电荷转移驱动自发光分解。我们的发现通过证明分子/金属氧化物界面中的双能量排列框架来调和长期存在的理论-实验差异：初始电荷捕获需要预捕获能量匹配，而通过化学中间体进行的捕获后稳定化会产生能量不对称，从而有效抑制载流子耗散。这种对界面电荷动力学的机理理解为高效光催化系统的合理开发提供了基本设计原则。
