Energy-Level Matching of Fe(III) Ions Grafted at Surface and Doped in Bulk for Efficient Visible-Light Photocatalysts
Energy-Level Matching of Fe(III) Ions Grafted at Surface and Doped in Bulk for Efficient Visible-Light Photocatalysts
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DOI：
10.1021/ja401541k
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发表时间：
2013-07-10
影响因子：
15
通讯作者：
Hashimoto, Kazuhito
中科院分区：
文献类型：
--
作者：
Liu, Min;Qiu, Xiaoqing;Hashimoto, Kazuhito
光催化反应速率（R）由光吸收能力（α）与量子效率（QE）相乘确定；然而，这两个参数通常存在权衡关系。因此，在不降低QE的情况下提高光催化效率仍然是开发具有高R的高效光催化剂的一个具有挑战性的问题。在此，使用Fe(III)离子接枝的Fe(III)掺杂TiO2作为模型系统，我们提出了一种开发具有高效R的可见光光催化剂的新方法，利用表面接枝的Fe(III)离子作为助催化剂和本体掺杂之间的能级匹配的概念 Fe(III) 离子作为可见光吸收剂。可见光下掺杂 Fe(III) 态的光生电子有效地转移到表面接枝 Fe(III) 离子助催化剂，因为大量掺杂 Fe(III) 离子产生的能级低于 TiO2 导带，与表面接枝 Fe(III) 离子中 Fe3+Fe2+ 氧化还原对的电势很好匹配。表面接枝的 Fe(III) 离子中的电子有效地引起吸附氧分子的多电子还原，从而实现高 QE 值。因此，本发明的 Fe(III)-FexTi1-xO2 纳米复合材料在先前报道的用于分解气态有机化合物的光催化剂中表现出最高的可见光 R。即使在商业白光发射二极管照射下也能实现高R，并且长期使用非常稳定，使其具有实用性。此外，这种有效的方法可以应用于其他宽带隙半导体，包括ZnO或SrTiO3，并且可能适用于其他光催化系统，例如水分解、CO2还原、NOx去除和染料分解。因此，该方法代表了开发实用新型可见光活性光催化剂的战略方法。
Photocatalytic reaction rate (R) is determined by the multiplication of light absorption capability (alpha) and quantum efficiency (QE); however, these two parameters generally have trade-off relations. Thus, increasing a without decreasing QE remains a challenging issue for developing efficient photocatalysts with high R. Herein, using Fe(III) ions grafted Fe(III) doped TiO2 as a model system, we present a novel method for developing visible-light photocatalysts with efficient R, utilizing the concept of energy level matching between surface-grafted Fe(III) ions as co-catalysts and bulk-doped Fe(III) ions as visible-light absorbers. Photogenerated electrons in the doped Fe(III) states under visible-light efficiently transfer to the surface grafted Fe(III) ions co-catalysts, as the doped Fe(III) ions in bulk produced energy levels below the conduction band of TiO2, which match well with the potential of Fe3+Fe2+ redox couple in the surface grafted Fe(III) ions. Electrons in the surface grafted Fe(III) ions efficiently cause multielectron reduction of adsorbed oxygen molecules to achieve high QE value. Consequently, the present Fe(III)-FexTi1-xO2 nanocomposites exhibited the highest visible-light R among the previously reported photocatalysts for decomposition of gaseous organic compounds. The high R can proceed even under commercial white-light emission diode irradiation and is very stable for long-term use, making it practically useful. Further, this efficient method could be applied in other wide-band gap semiconductors, including ZnO or SrTiO3, and may be potentially applicable for other photocatalysis systems, such as water splitting, CO2 reduction, NOx removal, and dye decomposition. Thus, this method represents a strategic approach to develop new visible-light active photocatalysts for practical uses.