Wang Jian, Perry Nicola H, Guo Liejin, Vayssieres Lionel, Tuller Harry L
International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering , Xi'an Jiaotong University , Xi'an 710049 , China.
Department of Materials Science & Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.
ACS Appl Mater Interfaces. 2019 Jan 16;11(2):2031-2041. doi: 10.1021/acsami.8b16911. Epub 2019 Jan 2.
Hematite (α-FeO) is regarded as one of the most promising cost-effective and stable anode materials in photoelectrochemical applications, and its performance, like other transition-metal oxides, depends strongly on its electrical and defect properties. In this work, the electrical and thermomechanical properties of undoped and Sn-doped α-FeO nanoscale powders were characterized in situ at controlled temperatures ( T = 250 to 400 °C) and atmospheres ( pO = 10 to 1 atm O) to investigate their transport and defect properties. Frequency-dependent complex impedance spectra show that interfacial resistance between particles is negligible in comparison with particle resistance. Detailed defect models predicting the dependence of electron, hole, and iron and oxygen vacancy concentrations on temperature and oxygen partial pressures for undoped and doped α-FeO were derived. Using these defect equilibria models, the operative defect regimes were established, and the bandgap energy of undoped α-FeO and oxidation enthalpy of Sn-doped α-FeO were obtained from the analysis of the temperature and pO dependence of the electrical conductivity. On the basis of these results, we are able to explain the surprisingly weak impact of donor doping on the electrical conductivity of α-FeO. Furthermore, experimental means based on the results of this study are given for successfully tuning hematite to enhance its photocatalytic activity for the water oxidation reaction.
赤铁矿（α-FeO）被认为是光电化学应用中最具前景的具有成本效益且稳定的阳极材料之一，并且与其他过渡金属氧化物一样，其性能在很大程度上取决于其电学和缺陷性质。在这项工作中，在可控温度（T = 250至400°C）和气氛（pO = 10至1 atm O）下对未掺杂和Sn掺杂的α-FeO纳米级粉末的电学和热机械性能进行了原位表征，以研究它们的输运和缺陷性质。频率相关的复阻抗谱表明，与颗粒电阻相比，颗粒间的界面电阻可忽略不计。推导了详细的缺陷模型，该模型预测了未掺杂和掺杂的α-FeO中电子、空穴以及铁和氧空位浓度对温度和氧分压的依赖性。利用这些缺陷平衡模型，确定了有效的缺陷区域，并通过分析电导率对温度和pO的依赖性，获得了未掺杂α-FeO的带隙能量和Sn掺杂α-FeO的氧化焓。基于这些结果，我们能够解释施主掺杂对α-FeO电导率的影响出奇地微弱。此外，基于本研究结果给出了成功调节赤铁矿以增强其水氧化反应光催化活性的实验方法。
