Lee Jaesang, Choi Wonyong
School of Environmental Science and Engineering and Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Korea.
J Phys Chem B. 2005 Apr 21;109(15):7399-406. doi: 10.1021/jp044425+.
Surface platinized TiO(2) (Pt/TiO(2)) has been frequently studied, but its photocatalytic reactivities reported in the literature are not consistent in some cases. To understand the discrepancies, the effects of Pt speciation on TiO(2) on the photocatalytic degradation (PCD) of a few chlorinated organic compounds (trichloroethylene (TCE), perchloroethylene (PCE), dichloroacetate, etc.) were investigated with several Pt/TiO(2) samples that were prepared differently. The oxidation state of Pt deposits was analyzed by X-ray photoelectron spectroscopy and was found to be the most important factor in determining the initial PCD rates of chlorinated organic compounds. TiO(2) with oxidized Pt species (Pt(ox)/TiO(2)) was less reactive than TiO(2) with metallic Pt (Pt(0)/TiO(2)) for all substrates tested. In particular, Pt(ox)/TiO(2) strongly inhibited the PCD of TCE and PCE whereas it was more reactive than pure TiO(2) for the PCD of other compounds. The photocurrents obtained with the Pt(ox)/TiO(2) electrode were lower than those with the Pt(0)/TiO(2) electrode, which was ascribed to the role of Pt(ox) species as a recombination center. It is proposed that TCE adsorbed on Pt(ox) chemically mediates the charge recombination through the redox cycle of TCE. The Pt effects in photocatalysis are highly substrate-specific and depend on the Pt-substrate interaction as well as the properties of Pt deposits.
表面镀铂的二氧化钛（Pt/TiO₂）已被广泛研究，但文献报道的其光催化反应活性在某些情况下并不一致。为了解这些差异，使用几种不同制备方法的Pt/TiO₂样品，研究了TiO₂上铂的形态对几种氯代有机化合物（三氯乙烯（TCE）、全氯乙烯（PCE）、二氯乙酸等）光催化降解（PCD）的影响。通过X射线光电子能谱分析了铂沉积物的氧化态，发现其是决定氯代有机化合物初始PCD速率的最重要因素。对于所有测试的底物，含有氧化态铂物种的TiO₂（Pt(ox)/TiO₂）的反应活性低于含有金属铂的TiO₂（Pt(0)/TiO₂）。特别是，Pt(ox)/TiO₂强烈抑制TCE和PCE的PCD，而对于其他化合物的PCD，它比纯TiO₂更具反应活性。Pt(ox)/TiO₂电极获得的光电流低于Pt(0)/TiO₂电极，这归因于Pt(ox)物种作为复合中心的作用。有人提出，吸附在Pt(ox)上的TCE通过TCE的氧化还原循环化学介导电荷复合。光催化中的铂效应具有高度的底物特异性，取决于铂与底物的相互作用以及铂沉积物的性质。
