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首页> 外文期刊>Journal of Materials Research >Enhanced water oxidation efficiency of hematite thin films by oxygen-deficient atmosphere
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Enhanced water oxidation efficiency of hematite thin films by oxygen-deficient atmosphere

机译：缺氧气氛提高赤铁矿薄膜的水氧化效率

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摘要

This work describes the effects of different atmospheres used during the thermal treatment of hematite films synthesized on transparent conductive substrates of fluorine-doped tin oxide by a newly reported wet chemical route assisted by microwave. The as-synthesized films were subjected to additional thermal treatment at 750 ℃ for 30 min in different gas flux (air, O_2, and N_2) to obtain a desirable phase and surface activation. A series of techniques were used to elucidate effects of each atmosphere used during the thermal treatment. The morphology of the films, as analyzed by top-view and cross-sectional scanning electron microscopy images, showed no significant changes and was composed of rods homogeneously distributed over the substrate, which covered the immersed area with a thickness between 98 and 100 nm. The photo-electrochemical response of the N_2-hematite films was found to be 80 and 50% more efficient at 1.23 V_(RHE) (reversible hydrogen electrode) than those of films produced in air and an O_2 atmosphere. The photocurrent enhancement achieved by treatment in an oxygen-deficient atmosphere was attributed to the improvement of hematite catalytic activity, which produced a hematite-electrolyte interface favorable for water oxidation. Since an increase in the donor density by one order of magnitude was found for the N_2-hematite films, a reduction of charge transfer resistance was expected in these films. However, the Nyquist plot analysis showed that the O_2-hematite film had a lower charge transfer resistance. As a result, it is impossible to relate the photocurrent enhancement observed in N_2-hematite film to electronic changes or vacancy formation, as previously reported in the literature. Indeed, by performing photoelectrochemical measurements in the presence of hole scavengers, it became clear that the major improvement caused by the oxygen-deficient atmosphere was in the catalytic activity efficiency of the hematite films for water oxidation. It was found that the oxygen-deficient atmosphere could improve the overall photoelectrochemical performance of the hematite by acting as a hole scavengers. This finding contrasts with a previous report, in which the use of an oxygen-deficient atmosphere during the phase transformation from akaganeite to hematite was found to enhance the photocurrent density by inducing an increased donor density caused by the formation of vacancies [Y. Ling et al., Angew. Chem., Int. Ed. 51, 4074 (2012)].
机译：这项工作描述了通过新报道的微波湿化学途径在掺氟氧化锡的透明导电基底上合成的赤铁矿薄膜热处理过程中使用的不同气氛的影响。合成后的薄膜在不同的气体通量（空气，O_2和N_2）中于750℃进行30分钟的额外热处理，以获得所需的相和表面活化。使用了一系列技术来阐明热处理过程中使用的每种气氛的影响。如通过顶视图和截面扫描电子显微镜图像分析的，膜的形态没有显示出明显变化，并且由均匀分布在基板上的棒组成，其覆盖了浸入区域，厚度在98至100nm之间。发现N_2-赤铁矿薄膜的光电化学反应在1.23 V_（RHE）（可逆氢电极）下的效率比在空气和O_2气氛中生产的薄膜高80％和50％。通过在缺氧气氛中处理而实现的光电流增强归因于赤铁矿催化活性的提高，从而产生了有利于水氧化的赤铁矿-电解质界面。由于发现N_2-赤铁矿薄膜的供体密度增加了一个数量级，因此预期这些薄膜的电荷转移电阻会降低。然而，奈奎斯特图分析表明，O_2-赤铁矿膜具有较低的电荷转移阻力。结果，如先前在文献中报道的，不可能将在N_2-赤铁矿膜中观察到的光电流增强与电子变化或空位形成相关联。实际上，通过在存在空穴清除剂的情况下进行光电化学测量，很明显，由缺氧气氛引起的主要改进在于赤铁矿膜对水氧化的催化活性效率。发现缺氧气氛可以通过充当空穴清除剂来改善赤铁矿的整体光电化学性能。这一发现与以前的报告形成了鲜明的对比，在以前的报告中，发现在从赤铁矿到赤铁矿的相变过程中使用缺氧气氛可以通过诱导空位形成引起的供体密度的增加来提高光电流密度[Y. Ling等，Angew。 Chem。，Int。埃德51，4074（2012）]。

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  • 来源
    《Journal of Materials Research》 |2015年第23期|3595-3604|共10页
  • 作者

    Andre L.M. Freitas; Waldemir M. Carvalho Jr.; Flavio L. Souza;

  • 作者单位

    Laboratory of Alternative Energy and Nanomaterial (LEAN), Centro de Ciencias Naturais e Humanas (CCNH), Universidade Federal do ABC (UFABC), Santo Andre, Sao Paulo 09210-580, Brazil;

    Laboratory of Alternative Energy and Nanomaterial (LEAN), Centro de Ciencias Naturais e Humanas (CCNH), Universidade Federal do ABC (UFABC), Santo Andre, Sao Paulo 09210-580, Brazil;

    Laboratory of Alternative Energy and Nanomaterial (LEAN), Centro de Ciencias Naturais e Humanas (CCNH), Universidade Federal do ABC (UFABC), Santo Andre, Sao Paulo 09210-580, Brazil;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
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  • 正文语种 eng
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