The spontaneous formation and long-term surface stabilization of superoxide radicals are observed on specific TiO₂ hybrid materials in which titanium is coordinated to an organic ligand. Here the rationale for this uncommon phenomenon is investigated by a synergistic theoretical and experimental approach involving density functional theory (DFT) calculations and spectroscopic techniques. Stoichiometric and reduced anatase (101) surfaces modified with acetylacetone, dibenzoylmethane, and catechol are comparatively examined. These results reveal that the interaction between organic ligands and adsorbed O₂ molecules improves when O vacancies are present on the external layer of the surface, promoting O₂ reduction. The electronic features of the ligand play a pivotal role for both an effective electronic interaction with the surface and the stabilization of the generated reactive oxygen species. These results agree with experimental data showing that sol–gel-derived Ti-diketonate hybrid oxides spontaneously produce very persistent superoxide radicals under ambient conditions, thus holding a high intrinsic oxidative activity.

中文翻译：

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在有机配体改性的氧化钛表面自发产生超稳定的活性氧物质

在特定的 TiO ₂杂化材料上观察到超氧自由基的自发形成和长期表面稳定，其中钛与有机配体配位。在这里，通过涉及密度泛函理论 (DFT) 计算和光谱技术的协同理论和实验方法研究了这种罕见现象的基本原理。对用乙酰丙酮、二苯甲酰甲烷和儿茶酚改性的化学计量和还原锐钛矿 (101) 表面进行了比较检查。这些结果表明，当表面外层存在 O 空位时，有机配体和吸附的 O ₂分子之间的相互作用得到改善，促进 O ₂减少。配体的电子特征对于与表面的有效电子相互作用和生成的活性氧的稳定都起着关键作用。这些结果与实验数据一致，表明溶胶-凝胶衍生的 Ti-二酮酸杂化氧化物在环境条件下自发产生非常持久的超氧自由基，从而保持高内在氧化活性。