Visible-light photocurrent response of TiO2-polyheptazine hybrids: evidence for interfacial charge-transfer absorption
Visible-light photocurrent response of TiO2-polyheptazine hybrids: evidence for interfacial charge-transfer absorption
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DOI：
10.1039/c1cp22861g
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发表时间：
2011-01-01
影响因子：
3.3
通讯作者：
Beranek, Radim
中科院分区：
文献类型：
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作者：
Bledowski, Michal;Wang, Lidong;Beranek, Radim
研究了基于tio2 -聚庚烷杂化材料的光电极。由于TiO2和聚庚嗪具有非常稳定的化学性质，因此它们是制造水光氧化光阳极的极有希望的候选材料。通过仔细分析光吸收光谱、发光特性和光电化学测量，实验确定了杂化物的性质，并通过量子化学计算加以证实。我们首次提供了清晰的实验证据，证明在聚七嗪（供体）和TiO2（受体）之间形成了一个界面电荷转移配合物，与这两个单一组分相比，这是导致杂化物吸收和光电流响应显著红移的原因。聚庚烷HOMO的光电荷直接转移到TiO2的导带边缘，形成以2.3 eV （540 nm）为中心的吸收带。光生成空穴的估计电位（+1.7 V vs. NHE, pH 7）允许水的光氧化（+0.82 V vs. NHE, pH 7），这可以通过可见光驱动（lambda > 420 nm）在IrO2纳米颗粒作为助催化剂修饰的杂化电极上进化得到证明。量子化学模拟表明，tio2 -聚七嗪界面是一个复杂而灵活的系统，有利于水氧化所需的质子转移过程。除了水分解之外，这种类型的混合材料还可以在太阳能转换和光响应器件的更广泛研究领域中找到进一步的应用。
We investigated photoelectrodes based on TiO2-polyheptazine hybrid materials. Since both TiO2 and polyheptazine are extremely chemically stable, these materials are highly promising candidates for fabrication of photoanodes for water photooxidation. The properties of the hybrids were experimentally determined by a careful analysis of optical absorption spectra, luminescence properties and photoelectrochemical measurements, and corroborated by quantum chemical calculations. We provide for the first time clear experimental evidence for the formation of an interfacial charge-transfer complex between polyheptazine (donor) and TiO2 (acceptor), which is responsible for a significant red shift of absorption and photocurrent response of the hybrid as compared to both of the single components. The direct optical charge transfer from the HOMO of polyheptazine to the conduction band edge of TiO2 gives rise to an absorption band centered at 2.3 eV (540 nm). The estimated potential of photogenerated holes (+1.7 V vs. NHE, pH 7) allows for photooxidation of water (+0.82 V vs. NHE, pH 7) as evidenced by visible light-driven (lambda > 420 nm) evolution of dioxygen on hybrid electrodes modified with IrO2 nanoparticles as a co-catalyst. The quantum-chemical simulations demonstrate that the TiO2-polyheptazine interface is a complex and flexible system energetically favorable for proton-transfer processes required for water oxidation. Apart from water splitting, this type of hybrid materials may also find further applications in a broader research area of solar energy conversion and photo-responsive devices.