Understanding the microscopic mechanism of water photocatalysis on TiO₂ is of great value in energy chemistry and catalysis. To date, it is still unclear how water photocatalysis occurs after the initial light absorption. Here we report the investigation of the photoinduced water dissociation and desorption on a R-TiO₂(110) surface, at different wavelengths (from 250 to 330 nm), using temperature-programmed desorption and time-of-flight techniques. Primary photooxidation products, gas phase OH radicals and surface H atoms, were clearly observed at wavelengths of ≤290 nm. As the laser wavelength decreases from 290 to 250 nm, the relative yield of H₂O oxidation increases significantly. Likewise, photoinduced H₂O desorption was also observed in the range of 320–250 nm, and the relative yield of H₂O desorption also increases with a decrease in wavelength. The strong wavelength-dependent H₂O photooxidation and photodesorption suggest that the energy of charge carriers is important in these two processes. More importantly, the result raises doubt about the widely accepted photocatalysis model of TiO₂ in which the excess energy of charge carriers is useless for photocatalysis. In addition, the H₂O photooxidation is more likely initiated by nonthermalized holes and is accomplished on the ground state potential energy surface via a non-adiabatic decay process.

中文翻译：

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金红石型TiO ₂（110）的波长依赖性水氧化

了解水在TiO ₂上的光催化作用的微观机理在能量化学和催化中具有重要的价值。迄今为止，尚不清楚在初始光吸收后水光催化如何发生。在这里，我们报告使用温度编程的解吸和飞行时间技术，对不同波长（从250至330 nm）的R-TiO ₂（110）表面上的光致水离解和解吸进行了研究。在≤290nm的波长下可以清楚地观察到主要的光氧化产物，气相OH自由基和表面H原子。随着激光波长从290 nm减小到250 nm，H ₂ O氧化的相对产率显着增加。同样，光诱导的H ₂在320-250 nm范围内也观察到O解吸，并且H ₂ O解吸的相对产率也随着波长的减小而增加。强烈的与波长有关的H ₂ O光氧化和光解吸表明，载流子的能量在这两个过程中很重要。更重要的是，该结果引起了人们对广泛接受的TiO ₂光催化模型的怀疑，在该模型中，电荷载流子的多余能量对光催化没有用。另外，H ₂ O的光氧化更可能由非热空穴引发，并通过非绝热衰变过程在基态势能表面上完成。