Role of Weakly Adsorbed Molecules in Catalytic Reactions

已观察到弱吸附的水显着增加铂/二氧化钛（Pt/TiO 2）催化剂上的有机物的光催化分解的速率，但化学吸附的水，这是更强的吸附，不。本研究的目的是了解弱吸附分子如何加速这些催化反应的速率。理解这些观察结果在许多催化反应中可能是重要的。这些研究也将有助于理解光催化氧化，用于氧化空气中低浓度的VOC污染物。 结合实验和理论的方法将被用来阐明这些催化反应的加速所涉及的机制。在室温下发生在Pt/TiO 2上的光催化分解是研究这种行为的特别有效的手段。使用紫外光来启动和停止反应等温提供了一个独特的手段来研究中间体和机制。实验研究将采用连续流等温反应、吸附物种和中间体的红外光谱以及程序升温脱附。瞬态等温反应将结合同位素标记作为实验研究的主要组成部分。水的吸附等温线将用于确定反应条件期间吸附的水量。 理论建模将使用从头计算化学来测试反应机理，确定弱吸附分子对吸附有机物的影响，并进行轨迹计算以研究光催化分解的反应坐标。优化的中间结构的红外光谱也将从第一原理计算与实验结果进行比较。建模和实验将相互协调，以便相互指导。

Weakly adsorbed water has been observed to dramatically increase the rates of photocatalytic decomposition of organics on platinum/titania (Pt/TiO2) catalysts, but chemisorbed water, which is more strongly adsorbed, does not. The objective of this research is to understand how weakly adsorbed molecules accelerate the rate of these catalytic reactions. Understanding these observations may be important in many catalytic reactions. These studies will also contribute to understanding photocatalytic oxidation, which is used to oxidize low concentrations of VOC pollutants in air. A combined experimental and theoretical approach will be used to elucidate the mechanisms that are involved in acceleration of these catalytic reactions. Photocatalytic decomposition, which takes place on Pt/TiO2 at room temperature, is a particularly effective means to study such behavior. The use of UV light to start and stop the reaction isothermally provides a unique means to study intermediates and mechanisms. The experimental studies will use continuous-flow isothermal reaction, infrared spectroscopy of adsorbed species and intermediates, and temperature-programmed desorption. Transient isothermal reaction will be combined with isotope labeling as a major component of the experimental studies. Adsorption isotherms of water will be used to determine the amounts of adsorbed water during reaction conditions. The theoretical modeling will use ab initio computational chemistry to test reaction mechanisms, determine the effect of weakly adsorbed molecules on adsorbed organics, and do trajectory calculations to investigate the reaction coordinate for photocatalytic decomposition. The infrared spectra of optimized intermediate structures will also be computed from first principles for comparison to the experimental results. The modeling and experiments will be coordinated so that each helps guide the other.