Abstract Nanostructured WO3 layers were obtained by one-step anodic oxidation of tungsten in an aqueous solution containing fluoride ions. A detailed investigation of the growth of anodic films on metallic substrate was focused on the study of the influence of anodization conditions, such as anodization potential, duration of the process, electrolyte composition, applied temperature, and electrolyte agitation on morphological features of as-received materials. Such kind of comprehensive studies has been performed for the first time. It was found that the optimal conditions allowing synthesis of nanostructures with well-defined pores and the thickest possible oxide layer are: anodization potential of 50 V, anodization time of 4 h, the electrolyte containing 1 M ammonium sulfate and 75 mM ammonium fluoride, temperature of 20 °C, and agitation of electrolyte of 250 rpm. A post-treatment procedure was developed to effectively remove the precipitates formed on the surface of anodic layers during anodization. The obtained materials were also examined as photoanodes in photoelectrochemical (PEC) water splitting experiments. It was confirmed, that PEC performance of nanostructured WO3 photoanodes can be significantly improved (higher photocurrents by 24%) after ultrasonic treatment in a 20 wt% HF solution for 10 s and ethanol for 5 s.

中文翻译：

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阳极氧化条件对水溶液中形成的多孔氧化钨层形貌的影响

摘要 通过在含有氟离子的水溶液中一步阳极氧化钨得到纳米结构的 WO3 层。对金属基材上阳极薄膜生长的详细研究集中在阳极氧化条件的影响上，如阳极氧化电位、过程持续时间、电解液成分、施加温度和电解液搅拌对原样形态特征的影响材料。此类综合研究尚属首次。发现允许合成具有明确孔隙和最厚氧化物层的纳米结构的最佳条件是：50 V 的阳极氧化电位、4 小时的阳极氧化时间、含有 1 M 硫酸铵和 75 mM 氟化铵的电解质、温度20°C，和电解液的搅拌速度为 250 rpm。开发了一种后处理程序，以有效去除阳极氧化过程中在阳极层表面形成的沉淀物。在光电化学（PEC）水分解实验中，还对获得的材料作为光阳极进行了检查。经证实，在 20 wt% HF 溶液中超声处理 10 秒和乙醇处理 5 秒后，纳米结构 WO3 光阳极的 PEC 性能可以显着提高（光电流提高 24%）。