Photoelectrochemical Water Splitting with Mesoporous Hematite Prepared by a Solution-Based Colloidal Approach
Photoelectrochemical Water Splitting with Mesoporous Hematite Prepared by a Solution-Based Colloidal Approach
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DOI：
10.1021/ja101564f
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发表时间：
2010-06-02
影响因子：
15
通讯作者：
Graetzel, Michael
中科院分区：
文献类型：
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作者：
Sivula, Kevin;Zboril, Radek;Graetzel, Michael
使用赤铁矿（α-Fe2O3）通过光电化学分解水来可持续生产氢气是太阳能化学存储的一种有前途的方法，但由于材料的非最佳光电特性而变得复杂。纳米结构方法已被证明可以提高赤铁矿的性能，但对所有吸收光波长都具有高效率的理想纳米结构仍然难以实现。在此，我们首次报道了采用溶液胶体法制备的介孔赤铁矿光电电极，在标准条件下（AM 1.5G 100 mW cm（-2），1.23 V vs 可逆氢电极，RHE）产生0.56 mA cm（-2）的水分解光电流，在暗电流开始前产生超过1.0 mA cm（-2）的光电流（1.55 V vs RHE）。发现烧结温度会增加平均粒径，并对光活性产生巨大影响。 X 射线光电子能谱和使用 SQUID 磁力计的磁性测量将这种效应与透明导电基板中掺杂剂原子的扩散和结合联系起来。此外，检查薄膜的光学特性表明，吸收系数和起始特性（赤铁矿作为太阳能转换器的关键方面）随烧结温度的变化而发生了相当大的变化。使用粉末 X 射线衍射和 Rietveld 精修对赤铁矿的晶体结构进行了详细研究，以解释这些效应，将 C-3v 型晶格畸变的增加与光学性能的改善相关联。
Sustainable hydrogen production through photoelectrochemical water splitting using hematite (alpha-Fe2O3) is a promising approach for the chemical storage of solar energy, but is complicated by the material's nonoptimal optoelectronic properties. Nanostructuring approaches have been shown to increase the performance of hematite, but the ideal nanostructure giving high efficiencies for all absorbed light wavelengths remains elusive. Here, we report for the first time mesoporous hematite photoelectodes prepared by a solution-based colloidal method which yield water-splitting photocurrents of 0.56 mA cm(-2) under standard conditions (AM 1.5G 100 mW cm(-2), 1.23 V vs reversible hydrogen electrode, RHE) and over 1.0 mA cm(-2) before the dark current onset (1.55 V vs RHE). The sintering temperature is found to increase the average particle size, and have a drastic effect on the photoactivity. X-ray photoelectron spectroscopy and magnetic measurements using a SQUID magnetometer link this effect to the diffusion and incorporation of dopant atoms from the transparent conducting substrate. In addition, examining the optical properties of the films reveals a considerable change in the absorption coefficient and onset properties, critical aspects for hematite as a solar energy converter, as a function of the sintering temperature. A detailed investigation into hematite's crystal structure using powder X-ray diffraction with Rietveld refinement to account for these effects correlates an increase in a C-3v-type crystal lattice distortion to the improved optical properties.