Mechanism of water photooxidation reaction at atomically flat TiO2 (rutile) (110) and (100) surfaces:: Dependence on solution pH
Mechanism of water photooxidation reaction at atomically flat TiO2 (rutile) (110) and (100) surfaces:: Dependence on solution pH
复制标题
原子平坦的二氧化钛（金红石型）（110）和（100）表面的水光氧化反应机理：： 溶液 pH 值的依赖性
DOI：
10.1021/ja073206
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发表时间：
2007-09-19
影响因子：
15
通讯作者：
Nakato, Yoshihiro
中科院分区：
文献类型：
--
作者：
Imanishi, Akihito;Okamura, Tomoaki;Nakato, Yoshihiro
采用光致发光（PL）技术研究了不同pH值水溶液中原子平面n-TiO2（金红石）表面的水光氧化反应机理。（1110）和（1100）表面的PL波段分别在810 nm和840 nm左右达到峰值，被分配到导电带电子和表面捕获空穴（STH）之间的辐射跃迁，[Ti-O=Ti-2](s)(+)，形成于表面晶格上的三配位（正常）0原子。PL强度（/(PL)）随着溶液pH的增加而逐渐降低，即在pH 4附近，TiO2的零电荷点附近急剧下降（约5），然后在pH 13附近迅速下降至零。第一次急剧下降是由于水分子对表面桥接氧（Ti-O-Ti）上的空穴的亲核攻击速率增加。密度的增加而增加博士亲核攻击被认为是主要的启动步骤水氧化反应低,中间博士高PL强度在低pH值是归因于缓慢的亲核攻击由于Ti-O-Ti密度非常低的质子化作用在低博士第二大幅降低pH值附近13是归因于表面形成阴离子物种像Ti-O photogenerated洞——这很容易氧化。讨论了本文提出的反应中间体与时间分辨激光光谱法报道的反应中间体之间的相互关系。
The mechanism of water photooxidation reaction at atomically flat n-TiO2 (rutile) surfaces was investigated in aqueous solutions of various pH values, using photoluminescence (PL) measurements. The PL bands, which peaked at around 810 and 840 nm for the (1110) and (1100) surfaces, respectively, were assigned to radiative transitions between conduction-band electrons and surface-trapped holes (STH), [Ti-O=Ti-2](s)(+), formed at triply coordinated (normal) 0 atoms at the surface lattice. The PL intensity (/(PL)) decreased stepwise with increasing solution pH, namely, it sharply decreased at around pH 4, near the point of zero charge of TiO2 (about 5), and then rapidly decreased to zero near pH 13. The first sharp decrease around pH 4 is attributed to the increased rate of nucleophilic attack of a water molecule to a hole at a site of surface bridging oxygen (Ti-O-Ti), the density of which increases with increasing pH. The nucleophilic attack is regarded as the main initiating step of the water oxidation reaction in low and intermediate pH. The high PL intensity at low pH is ascribed to slow nucleophilic attack owing to a very low density of Ti-O-Ti by its protonation at the low pH. The second sharp decrease near pH 13 is attributed to formation of surface anionic species like Ti-O- which can be readily oxidized by photogenerated holes. Interrelations between reaction intermediates proposed in this work and those reported by time-resolved laser spectroscopy are discussed.