Copper-Intercalated Birnessite as a Water Oxidation Catalyst.
Copper-Intercalated Birnessite as a Water Oxidation Catalyst.
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DOI：
10.1021/acs.langmuir.5b02936
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发表时间：
2015-11
期刊：
影响因子：
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通讯作者：
Akila C. Thenuwara;S. L. Shumlas;N. Attanayake;Elizabeth B. Cerkez;I. McKendry;Laszlo Frazer;E. Borguet-E.-Bo
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文献类型：
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作者：
Akila C. Thenuwara;S. L. Shumlas;N. Attanayake;Elizabeth B. Cerkez;I. McKendry;Laszlo Frazer;E. Borguet-E.-Bo
本文报道了一种通过在层状锰氧化物的层间区域插入铜来提高水钠锰矿对水氧化的催化活性的合成方法。通过XRD、XPS、ICP和拉曼光谱验证的铜的插层通过将水钠锰矿的悬浮液暴露于在溶液中经历插层以产生Cu（0）和Cu（2+）的含Cu（+）的前体分子来完成。电催化研究表明，铜改性的水钠锰矿表现出的水氧化的过电位为490 mV（在10 mA/cm（2））和塔菲尔斜率为126 mV/decade相比，分别为700 mV（在10 mA/cm（2））和240 mV/decade，没有铜的水钠锰矿。阻抗谱结果表明，铜改性的样品的电荷转移电阻率显着低于无Cu的水钠锰矿，这表明在中间层中的Cu增加了水钠锰矿的导电性，导致水氧化动力学的增强。密度泛函理论计算表明，Cu（0）嵌入到层状MnO 2模型结构中导致材料的电子性质从半导体结构转变为类金属结构.这一计算结论与上述阻抗谱结果基本一致。X射线光电子能谱（XPS）分析表明，Cu改性水钠锰矿中Cu（0）与Cu（2+）共存。使用仅用Cu（2+）修饰的水钠锰矿的对照实验显示水氧化动力学降低，进一步强调了Cu（0）对于水钠锰矿活性增加的重要性。在水钠锰矿结构中引入Cu（0）也增加了电催化剂的稳定性。在2 mA的工作电流下，与当Cu不存在于水钠锰矿中时相比，Cu改性的水钠锰矿使水氧化的过电位增加100 mV所需的时间长103倍。
We report a synthetic method to increase the catalytic activity of birnessite toward water oxidation by intercalating copper in the interlayer region of the layered manganese oxide. Intercalation of copper, verified by XRD, XPS, ICP, and Raman spectroscopy, was accomplished by exposing a suspension of birnessite to a Cu(+)-bearing precursor molecule that underwent disproportionation in solution to yield Cu(0) and Cu(2+). Electrocatalytic studies showed that the Cu-modified birnessite exhibited an overpotential for water oxidation of ∼490 mV (at 10 mA/cm(2)) and a Tafel slope of 126 mV/decade compared to ∼700 mV (at 10 mA/cm(2)) and 240 mV/decade, respectively, for birnessite without copper. Impedance spectroscopy results suggested that the charge transfer resistivity of the Cu-modified sample was significantly lower than Cu-free birnessite, suggesting that Cu in the interlayer increased the conductivity of birnessite leading to an enhancement of water oxidation kinetics. Density functional theory calculations show that the intercalation of Cu(0) into a layered MnO2 model structure led to a change of the electronic properties of the material from a semiconductor to a metallic-like structure. This conclusion from computation is in general agreement with the aforementioned impedance spectroscopy results. X-ray photoelectron spectroscopy (XPS) showed that Cu(0) coexisted with Cu(2+) in the prepared Cu-modified birnessite. Control experiments using birnessite that was decorated with only Cu(2+) showed a reduction in water oxidation kinetics, further emphasizing the importance of Cu(0) for the increased activity of birnessite. The introduction of Cu(0) into the birnessite structure also increased the stability of the electrocatalyst. At a working current of 2 mA, the Cu-modified birnessite took ∼3 times longer for the overpotential for water oxdiation to increase by 100 mV compared to when Cu was not present in the birnessite.