Nakamura Ryuhei, Nakato Yoshihiro
Division of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
J Am Chem Soc. 2004 Feb 4;126(4):1290-8. doi: 10.1021/ja0388764.
Primary intermediates of oxygen photoevolution (water photooxidation) reaction at the TiO2 (rutile)/aqueous solution interface were investigated by in situ multiple internal reflection infrared (MIRIR) absorption and photoluminescence (PL) measurements. UV irradiation of TiO2 in the presence of 10 mM Fe3+ in the solution caused the appearance of a new peak at 838 cm(-1) and a shoulder at 812 cm(-1). Detailed investigations of the effects of solution pH, the presence of methanol as a hole scavenger, and isotope exchange in water (H2(16)O-->H2(18)O) on the spectra have shown that the 838- and 812-cm(-1) bands can be assigned to the O-O stretching mode of surface TiOOH and TiOOTi, respectively, produced as primary intermediates of the oxygen photoevolution reaction. The results give strong support to our previously proposed mechanism that the oxygen photoevolution is initiated by a nucleophilic attack of a H2O molecule on a photogenerated hole at a surface lattice O site, not by oxidation of surface OH group by the hole. The conclusion is supported by PL measurements. A plausible reaction scheme is proposed for the oxygen photoevolution on TiO2 (rutile) in aqueous solutions of pH less than about 12.
通过原位多重内反射红外（MIRIR）吸收和光致发光（PL）测量，研究了TiO₂（金红石）/水溶液界面处氧光解（水光氧化）反应的主要中间体。在溶液中存在10 mM Fe³⁺的情况下对TiO₂进行紫外线照射，导致在838 cm⁻¹处出现一个新峰，在812 cm⁻¹处出现一个肩峰。对溶液pH值、作为空穴清除剂的甲醇的存在以及水中同位素交换（H₂¹⁶O→H₂¹⁸O）对光谱影响的详细研究表明，838 cm⁻¹和812 cm⁻¹处的谱带可分别归属于表面TiOOH和TiOOTi的O - O伸缩模式，它们是氧光解反应的主要中间体。这些结果有力地支持了我们先前提出的机制，即氧光解是由H₂O分子对表面晶格O位点处的光生空穴进行亲核攻击引发的，而不是由空穴氧化表面OH基团引发的。该结论得到了PL测量的支持。针对pH小于约12的水溶液中TiO₂（金红石）上的氧光解，提出了一个合理的反应方案。
