利用时间分辨相干反斯托克斯拉曼散射技术研究光催化产氢反应动力学

基于飞秒再生放大器及飞秒光学参量放大器输出的激光脉冲, 搭建了宽带时间分辨相干反斯托克斯拉曼散射(CARS)测试装置, 并利用该装置研究了氢气与空气混合气体中氢气的相对含量, 探测相对延时与CARS光谱之间的关系. 通过调整延时, 获得了无非共振背景干扰的氢气CARS信号. 实验中测得的CARS信号强度与氢气浓度(分压)的平方呈良好的线性关系, 符合CARS理论预测. 同时测得的实验数据的信噪比表明: 在当前的实验条件下, 在氢气与空气混合气的总压为0.1 MPa时, 该装置可以对氢气的浓度进行测量, 且其检测极限可低至0.2%. 本文还利用该装置对三联吡啶苯乙炔Pt 配合物-Co 配合物-三乙醇胺(TEOA)的三元化学催化体系的产氢动力学行为进行了研究, 通过改变pH值讨论了该催化体系的产氢动力学机制. 结果表明过高的质子浓度会降低体系的产氢效率, 这可能是因为在酸性条件下, 作为质子和电子供体的三乙醇胺分解被抑制, 电子供应中断, 导致产氢反应的停止.

Application of Time-Resolved Coherent Anti-Stokes Raman Scattering Technique on the Study of Photocatalytic Hydrogen Production Kinetics

Based on the laser pulse output from a femtosecond regenerative amplifier and optical parametric amplifier (OPA), a broadband time-resolved coherent anti-Stokes Raman scattering (CARS) setup was assembled. Using this setup, the relationship of hydrogen CARS spectra to its amount in a mixture with air and the relevant detection time-delay were studied. Hydrogen CARS spectra without nonresonant background interference were obtained by adjusting the detection time-delay. The observed CARS intensity exhibited a linear relationship with the square of hydrogen concentration, which is consistent with the theoretical prediction. The signal-to-noise ratio showed that when the pressure of hydrogen-air mixed gas was 0.1 MPa, the detection limit of our setup was less than 0.2%. Using this setup, the hydrogen production kinetics of a platinum(II) terpyridyl acetylide molecular-cobalt catalysttriethanolamine (TEOA) system was studied. The kinetic mechanism of hydrogen production was discussed by considering the effect of changing pH. The results indicate that a high proton concentration will reduce the hydrogen production efficiency. This can be attributed to the inhibition of hydrolysis of TEOA under acidic conditions, because it is the electron and proton donor in this hydrogen production system.