A Facile Surface Passivation of Hematite Photoanodes with TiO2 Overlayers for Efficient Solar Water Splitting
A Facile Surface Passivation of Hematite Photoanodes with TiO2 Overlayers for Efficient Solar Water Splitting
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DOI：
10.1021/acsami.5b07065
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发表时间：
2015-11-04
影响因子：
9.5
通讯作者：
Bahnemann, Detlef W.
中科院分区：
文献类型：
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作者：
Ahmed, Mahmoud G.;Kretschmer, Imme E.;Bahnemann, Detlef W.
最近，用钝化层对半导体光电极进行表面修饰作为改善半导体液体界面上的电荷分离和电荷转移过程的有效策略而引起了极大的关注。它通常通过采用复杂的原子层沉积技术来进行，该技术依赖于反应性且昂贵的金属有机化合物和真空处理，这两者都是大规模应用的重大障碍。本文开发了一种简便的水基溶液方法，使用水溶性钛络合物（即二氢氧化钛双（乳酸铵），TALH）对纳米结构赤铁矿光电阳极进行 TiO2 覆盖层的改性。通过X射线衍射、扫描电子显微镜和X射线光电子能谱对由此制备的纳米结构赤铁矿光阳极进行了表征。光电化学测量表明，用 TiO2 覆盖层修饰的纳米结构赤铁矿光阳极表现出约 100 nm 的光电流响应。比在标准照明条件下测量的裸露赤铁矿光电阳极（即0.27 mA cm(-2) vs RHE）高4.5倍（即1.2 mA cm(-2) vs RHE）。此外，约的阴极转变。水氧化起始电位达到190 mV。基于稳态偏振、瞬态光电流响应、开路电位、强度调制光电流光谱和阻抗光谱测量，对这些结果进行了讨论和探索。结论是TiO2覆盖层钝化了表面态并抑制了表面电子空穴复合，从而增加了产生的光电压和能带弯曲。目前用 TiO2 覆盖层修饰赤铁矿电极的方法有效且简单，可能在稳定和高性能光电极的开发中得到广泛的应用。
The surface modification of semiconductor photoelectrodes with passivation overlayers has recently attracted great attention as an effective strategy to improve the charge-separation and charge-transfer processes across semiconductor liquid interfaces. It is usually carried out by employing the sophisticated atomic layer deposition technique, which relies on reactive and expensive metalorganic compounds and vacuum processing, both of which are significant obstacles toward large-scale applications. In this paper, a facile water-based solution method has been developed for the modification of nanostructured hematite photoanode with TiO2 overlayers using a water-soluble titanium complex (i.e., titanium bis(ammonium lactate) dihydroxide, TALH). The thus-fabricated nanostructured hematite photoanodes have been characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Photoelectrochemical measurements indicated that a nanostructured hematite photoanodes modified with a TiO2 overlayer exhibited a photocurrent response ca. 4.5 times higher (i.e., 1.2 mA cm(-2) vs RHE) than that obtained on the bare hematite photoanode (i.e., 0.27 mA cm(-2) vs RHE) measured under standard illumination conditions. Moreover, a cathodic shift of ca. 190 mV in the water oxidation onset potential was achieved. These results are discussed and explored on the basis of steady-state polarization, transient photocurrent response, open-circuit potential, intensity-modulated photocurrent spectroscopy, and impedance spectroscopy measurements. It is concluded that the TiO2 overlayer passivates the surface states and suppresses the surface electron hole recombination, thus increasing the generated photovoltage and the band bending. The present method for the hematite electrode modification with a TiO2 overlayer is effective and simple and might find broad applications in the development of stable and high-performance photoelectrodes.