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Solar active heterojunction of p-CaFe2O4/n-ZnO for photoredox reactions
Environmental Technology & Innovation ( IF 6.7 ) Pub Date : 2020-07-22 , DOI: 10.1016/j.eti.2020.101060
E.T. Anthony , I.A. Lawal , M.O. Bankole , M. Klink , I.A. Ololade , N.A. Oladoja

In order to enable the solar activity of ZnO and to reduce the rate of recombination of the electron–hole in the use of Ca ferrite for photoredox reaction, heterojunction composite of these two semiconductors was prepared and characterized. The solar activity of the heterojunction was determined in two separate synthetic waste waters containing Rhodamine B (RhB) and Cr (VI). The underlying mechanisms of the RhB decolourization/mineralization and Cr (VI) reduction to Cr (III) were elucidated. Within the calcination temperature and precursors combination ratios (i.e. Ca Ferrite and ZnO ratio) studied, the optimum photoredox efficiency was achieved at 500 °C and precursors combination ratio of 1:1. The SEM analysis and elemental mapping showed an even dispersion of the precursors mix. The presence of Ca Ferrite conferred solar activity and narrowed the band gap of the heterojunction. The photoluminescence spectra and electro impedance spectra showed that the recombination rate of the heterojunction was lowered than that of any of the precursors. The fitting of the time–concentration profiles of the RhB decolourization/mineralization and Cr(VI) reduction to the pseudo first order kinetic equation showed that the values of the rate constants greatly depended on the initial pollutant concentrations. While all the generated reactive species were found to be responsible for the decolourization/mineralization of RhB, the superoxide was the sole reactive species ascertained for the Cr (VI) reduction to Cr (III).



中文翻译:

p-CaFe 2 O 4 / n-ZnO的太阳活性异质结用于光氧化还原反应

为了使ZnO具有太阳能活性,并在使用Ca铁氧体进行光氧化还原反应时降低电子-空穴的复合速率,制备并表征了这两种半导体的异质结复合材料。在含有罗丹明B(RhB)和Cr(VI)的两个单独的合成废水中测定了异质结的太阳活动。阐明了RhB脱色/矿化和Cr(VI)还原为Cr(III)的潜在机理。在所研究的煅烧温度和前驱体混合比(即钙铁氧体和ZnO的比例)内,最佳光氧化还原效率在500°C和前驱体混合比为1:1的条件下实现。SEM分析和元素图谱显示前体混合物均匀分散。Ca铁氧体的存在赋予了太阳活动并缩小了异质结的带隙。光致发光光谱和电阻抗光谱表明,异质结的复合率比任何前体的复合率都低。RhB脱色/矿化和Cr(VI)还原的时间-浓度曲线与拟一级动力学方程的拟合表明,速率常数的值很大程度上取决于初始污染物浓度。虽然发现所有产生的反应性物质都导致RhB的脱色/矿化,但超氧化物是确定的唯一的反应性物质,可将Cr(VI)还原为Cr(III)。光致发光光谱和电阻抗光谱表明,异质结的复合率比任何前体的复合率都低。RhB脱色/矿化和Cr(VI)还原的时间-浓度曲线与拟一级动力学方程的拟合表明,速率常数的值很大程度上取决于初始污染物浓度。虽然发现所有生成的反应性物质都导致RhB的脱色/矿化,但超氧化物是确定的唯一的反应性物质,可将Cr(VI)还原为Cr(III)。光致发光光谱和电阻抗光谱表明,异质结的复合率比任何前体的复合率都低。RhB脱色/矿化和Cr(VI)还原的时间-浓度曲线与拟一级动力学方程的拟合表明,速率常数的值很大程度上取决于初始污染物浓度。虽然发现所有产生的反应性物质都导致RhB的脱色/矿化,但超氧化物是确定的唯一的反应性物质,可将Cr(VI)还原为Cr(III)。RhB脱色/矿化和Cr(VI)还原的时间-浓度曲线与拟一级动力学方程的拟合表明,速率常数的值很大程度上取决于初始污染物浓度。虽然发现所有产生的反应性物质都导致RhB的脱色/矿化,但超氧化物是确定的唯一的反应性物质,可将Cr(VI)还原为Cr(III)。RhB脱色/矿化和Cr(VI)还原的时间-浓度曲线与拟一级动力学方程的拟合表明,速率常数的值很大程度上取决于初始污染物浓度。虽然发现所有产生的反应性物质都导致RhB的脱色/矿化,但超氧化物是确定的唯一的反应性物质,可将Cr(VI)还原为Cr(III)。

更新日期:2020-07-24
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