Electrochemical and photoelectrochemical investigation of single-crystal anatase
Electrochemical and photoelectrochemical investigation of single-crystal anatase
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DOI：
10.1021/ja954172l
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发表时间：
1996-07-17
影响因子：
15
通讯作者：
Scheel, HJ
中科院分区：
文献类型：
--
作者：
Kavan, L;Gratzel, M;Scheel, HJ
以TeCl4为输运剂，通过化学输运反应生长出含0.22% Al和微量V、Zr、Nb、La的TiO2锐钛矿单晶。采用掺杂氢还原的（101）面暴露电极，首次研究了锐钛矿单晶的电化学和光电化学行为。将其性能与暴露（001）表面的单晶金红石进行了比较。阻抗分析表明锐钛矿（101）的平带电位比金红石（001）的平带电位负移0.2 V。正偏压下的界面电容测量表明锐钛矿表面状态的密度较小。在λ = 300 nm处，金红石和锐钛矿都发生了水的光电氧化，入射光子-电流转换效率接近于1。从U-fb和E(g)的比较可以看出，锐钛矿（101）和金红石（001）电极的主要区别在于导带边缘的位置。从热力学上讲，只有锐钛矿才能将水完全光解为H-2和O-2。吸附顺式ru [L(2)(SCN)(2)] （L=2,2'-联吡啶-4,4'-二羧酸）的光敏电子注入在两种类型的电极上都具有相似的效率。然而，与纳米锐钛矿薄膜相比，单晶电极上的光诱导电荷分离效率大约低三倍。锐钛矿（101）对Li+的电化学插入比金红石（001）明显更活跃。Li+插入和提取的扩散系数分别为2 × 10（-13）和6 × 10(-13) cm(2)/s。
Single crystals of TiO2 anatase containing 0.22% of Al and traces of V, Zr, Nb, and La were grown by chemical transport reactions employing TeCl4 as the transporting agent. Electrodes having the (101) face exposed doped by reduction with hydrogen were employed, The electrochemical and photoelectrochemical behavior of a single crystal of anatase were scrutinized for the first time. Properties were compared to those of single-crystal rutile having the (001) face exposed. Impedance analysis established that the flatband potential of anatase (101) is shifted negatively by 0.2 V with regards to that of rutile (001). Interfacial capacitance measurements under forward bias indicate smaller density bf surface states on anatase. Photoelectrochemical oxidation of water occurs on both rutile and anatase with incident photon-to-current conversion efficiencies close to unity at lambda = 300 nm. From the comparison of U-fb and E(g), it follows that anatase (101) and rutile (001) electrodes differ mainly in the position of the conduction band edge. The complete photoelectrolysis of water to H-2 and O-2 is thermodynamically possible on anatase only. Photosensitized electron injection from adsorbed cis-Ru[L(2)(SCN)(2)] (L=2,2'-bipyridyl-4,4'-dicarboxylic acid) proceeds with similar efficiency on both types of electrodes. However, light-induced charge separation on the single-crystal electrodes is about three times less efficient compared with nanoscopic anatase films. Anatase (101) is strikingly more active for electrochemical insertion of Li+ than rutile (001). The diffusion coefficients for Li+ insertion and extraction were estimated to be 2 x 10(-13) and 6 x 10(-13) cm(2)/s, respectively.