Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.
J Am Chem Soc. 2009 Mar 11;131(9):3216-24. doi: 10.1021/ja806719x.
It is fundamentally interesting to study the photoelectrochemical properties of complex oxides for applications in photovoltaics and photocatalysis. In this paper, we study the band gap (E(g)) and energetics of the conduction band (CB) and valence band (VB) for films of zinc stannate (Zn(2)SnO(4)) nanoparticles (ca. 25 nm) of the inverse-spinel structure prepared by the hydrothermal method. UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemistry, and photoelectrochemistry were used to study the films. The fundamental E(g) for Zn(2)SnO(4) is proposed to be 3.6-3.7 eV with a direct-forbidden transition. The position of the CB was approximated from the flat band potential, E(fb), measured by the photocurrent onset potential. In aqueous and nonaqueous solutions the E(fb) of n-Zn(2)SnO(4) was found to be more positive than TiO(2) anatase in the electrochemical scale. In aqueous solutions E(fb) of Zn(2)SnO(4) was found to follow a 59 mV/pH slope with E(fb) extrapolated at pH 0 of 0.08 V vs NHE. In acetonitrile solutions that simulate the electrolyte for dye-sensitized solar cells (DSCs) the E(fb) of Zn(2)SnO(4) was found to be strongly dependent on electrolyte composition and more positive than TiO(2) vs the I(-)/I(3)(-) couple. The reverse trend observed for the open-circuit voltage in certain DSC electrolytes is explained in terms of the higher rates of electron-triiodide recombination of TiO(2) despite the lower position of the Zn(2)SnO(4) CB in the vacuum scale.
研究复杂氧化物的光电化学性质对于光伏和光催化应用具有重要意义。本文研究了通过水热法制备的反尖晶石结构的锌锡氧化物（Zn2SnO4）纳米颗粒（约 25nm）薄膜的带隙（Eg）和导带（CB）和价带（VB）的能级。使用紫外可见光谱、X 射线衍射（XRD）、扫描电子显微镜（SEM）、电化学和光电化学研究了这些薄膜。提出 Zn2SnO4 的基本 Eg 为 3.6-3.7eV，具有直接禁带跃迁。通过光电流起始电位测量的平带电位（EfB）来近似 CB 的位置。在水溶液和非水溶液中，n-Zn2SnO4 的 EfB 在电化学尺度上比锐钛矿 TiO2 更正。在水溶液中，Zn2SnO4 的 EfB 发现遵循 59mV/pH 斜率，在 pH0 时 EfB 外推值为 0.08V 相对于 NHE。在模拟染料敏化太阳能电池（DSC）电解质的乙腈溶液中，Zn2SnO4 的 EfB 发现强烈依赖于电解质组成，相对于 I-/I3-电对比 TiO2 更正。在某些 DSC 电解质中观察到的开路电压的反向趋势可以用 TiO2 的电子-三碘化物复合速率较高来解释，尽管 Zn2SnO4 的 CB 在真空尺度上的位置较低。
