Photocatalytic activity of TiO2-WO3 mixed oxides in relation to electron transfer efficiency
Photocatalytic activity of TiO2-WO3 mixed oxides in relation to electron transfer efficiency
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DOI：
10.1016/j.apcatb.2016.01.004
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发表时间：
2016-06
影响因子：
22.1
通讯作者：
M. Dozzi;S. Marzorati;M. Longhi;M. Coduri;L. Artiglia;E. Selli
中科院分区：
文献类型：
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作者：
M. Dozzi;S. Marzorati;M. Longhi;M. Coduri;L. Artiglia;E. Selli
为了制备具有最小化光生电子-空穴对复合的光催化剂，采用碱催化溶胶-凝胶法，通过偶联TiO 2和不同量的WO 3，制备了一系列Ti-W复合氧化物。通过表面和本体技术表征光催化剂，并在氧化和还原光催化反应、甲酸（FA）矿化和Cr（VI）还原中进行测试。i.e.in钨主要存在于TiO 2表面的六方晶系WO 3，虽然一小部分的W迁移到TiO 2晶格取代Ti原子，证明了由XRPD分析。不同的光活性尺度被发现在两个测试反应，都发生在相同的pH值范围内类似的基板光催化剂的静电相互作用。事实上，光激发电子从TiO 2的导带（CB）转移到耦合WO 3的CB，在能量上不能还原O2分子，很容易与光生空穴复合，从而导致FA光矿化的光活性随着W/Ti比的增加而降低。相反，将TiO 2与少量WO 3（0.2-1.0 mol%）偶联有利于去除Cr2 O 72 −阴离子。这些物种的特征在于氧化还原电位比WO 3的CB边缘更正，可以有效地接受WO 3域中捕获的电子，转化为毒性较小的Cr（III）物种。因此，WO 3表面域有效地促进光生电荷分离，有效地捕获CB电子，增加光催化效率取决于直接（或间接）参与光催化过程中的电子受体物种的氧化还原电位。
Aiming at producing photocatalysts with minimized photoproduced electron – hole pairs recombination, a series of titanium – tungsten mixed oxides has been prepared, by coupling TiO2with different amounts of WO3, according to an alkaline-catalyzed sol-gel method followed by an incipient wetting procedure. The photocatalysts were characterized by surface and bulk techniques and tested in both an oxidation and a reduction photocatalytic reaction,i.e.in formic acid (FA) mineralization and in Cr(VI) reduction. Tungsten was mainly present as hexagonal WO3on the TiO2surface, though a fraction of W migrates into the TiO2lattice substituting Ti atoms, as evidenced by XRPD analysis. Different photoactivity scales were found in the two test reactions, both occurring in the same pH range under similar substrate-photocatalyst electrostatic interactions. In fact, photoexcited electrons transferred from the conduction band (CB) of TiO2to the CB of coupled WO3, being energetically unable to reduce O2molecules, easily recombine with photoproduced holes, with a consequent photoactivity decrease in FA photo-mineralization with increasing W/Ti ratio. On the contrary, coupling TiO2with small WO3amounts (0.2–1.0 mol%) is beneficial in the removal of Cr2O72−anions. These species, being characterized by a redox potential more positive than the CB edge of WO3, may efficiently accept the electrons trapped in WO3domains, converting into less toxic Cr(III) species. Thus, WO3surface domains effectively promote photoproduced charge separation by efficiently trapping CB electrons; increased photocatalytic efficiency depends on the redox potential of the electron acceptor species directly (or indirectly) involved in the photocatalytic process.