We report significant photoelectrochemical activity of Y-doped BiFeO3 (Y-BFO) epitaxial thin films deposited on Nb:SrTiO3 substrates. The Y-BFO photoanodes exhibit a strong dependence of the photocurrent values on the thickness of the films, and implicitly on the induced epitaxial strain. The peculiar crystalline structure of the Y-BFO thin films and the structural changes after the PEC experiments have been revealed by high resolution X-ray diffraction and transmission electron microscopy investigations. The crystalline coherence breaking due to the small ionic radius Y-addition was analyzed using Willliamson-Hall approach on the 2θ-ω scans of the symmetric (00 l) reflections and confirmed by high resolution TEM (HR-TEM) analysis. In the thinnest sample the lateral coherence length (L∥) is preserved on larger nanoregionsanodomains. For higher thickness values L∥ is decreasing while domains tilt angles (αtilt) is increasing. The photocurrent value obtained for the thinnest sample was as high as Jph = 0.72 mA/cm2, at 1.4 V(vs. RHE). The potentiostatic scans of the Y-BFO photoanodes show the stability of photoresponse, irrespective of the film’s thickness. There is no clear cathodic photocurrent observation for the Y-BFO thin films confirming the n-type semiconductor behavior of the Y-BFO photoelectrodes.
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机译:我们报告沉积在Nb:SrTiO3衬底上的掺Y的BiFeO3(Y-BFO)外延薄膜具有显着的光电化学活性。 Y-BFO光电阳极显示出光电流值对薄膜厚度的强烈依赖性,并隐含地依赖于诱导的外延应变。通过高分辨率X射线衍射和透射电子显微镜研究揭示了Y-BFO薄膜的独特晶体结构和PEC实验后的结构变化。使用Willliamson-Hall方法在对称(00 l)反射的2θ-ω扫描上分析了由于离子半径Y加成小而导致的晶体相干破裂,并通过高分辨率TEM(HR-TEM)分析得到了证实。在最薄的样品中,横向相干长度(L 1)保留在较大的纳米区域/纳米域上。对于较高的厚度,L 1减小,而畴的倾斜角(α倾斜)增大。在1.4 V(vs。RHE)下,最薄样品的光电流值高达Jph = 0.72 mA / cm 2 sup>。 Y-BFO光阳极的恒电位扫描显示了光响应的稳定性,而与膜的厚度无关。对于Y-BFO薄膜没有清晰的阴极光电流观察,证实了Y-BFO光电极的n型半导体行为。
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