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焦磷酸铜络合物还原过程中要经过一价铜这个中间产物在一些文献中都假设过。这个问题不仅是有兴趣的理论问题,而且也很有实际价值。因为在工业电镀中经常出现的所谓“铜粉”,常常影响镀层的质量。简单的Cu~(2+)离子在氧化物溶液中进行阴极还原时,曾经用旋转圆环-圆盘电极(RRDE)的方法实验证实了一价铜中间产物的存在。但是在铜以络离子存在时,尤其是在过剩的焦磷酸离子存在下,使得还原在较负的电位下进行。这时是否有一价铜中间产物,尚未见到RRDE的研究。用RRDE研究络离子还原的工作还很少。可是这一有力方法的应用将会揭示许多一般方 相似文献
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龚演 郭景文 李佳恒 朱科静 廖孟涵 刘效治 张庆华 谷林 唐林 冯硝 张定 李渭 宋灿立 王立莉 于浦 陈曦 王亚愚 姚宏 段文晖 徐勇 张首晟 马旭村 薛其坤 何珂 《中国物理快报》2019,(7)
An intrinsic magnetic topological insulator(TI) is a stoichiometric magnetic compound possessing both inherent magnetic order and topological electronic states. Such a material can provide a shortcut to various novel topological quantum effects but remained elusive experimentally for a long time. Here we report the experimental realization of thin films of an intrinsic magnetic TI, MnBi_2Te_4, by alternate growth of a Bi_2Te_3 quintuple layer and a MnTe bilayer with molecular beam epitaxy. The material shows the archetypical Dirac surface states in angle-resolved photoemission spectroscopy and is demonstrated to be an antiferromagnetic topological insulator with ferromagnetic surfaces by magnetic and transport measurements as well as first-principles calculations. The unique magnetic and topological electronic structures and their interplays enable the material to embody rich quantum phases such as quantum anomalous Hall insulators and axion insulators at higher temperature and in a well-controlled way. 相似文献
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Quantum anomalous Hall(QAH) effect is a quantum Hall effect that occurs without the need of external magnetic field. A system composed of multiple parallel QAH layers is an effective high Chern number QAH insulator and the key to the applications of the dissipationless chiral edge channels in low energy consumption electronics. Such a QAH multilayer can also be engineered into other exotic topological phases such as a magnetic Weyl semimetal with only one pair of Weyl points. This work reports the first experimental realization of QAH multilayers in the superlattices composed of magnetically doped(Bi,Sb)_2Te_3 topological insulator and Cd Se normal insulator layers grown by molecular beam epitaxy. The obtained multilayer samples show quantized Hall resistance h/N_e~2, where h is Planck's constant, e is the elementary charge and N is the number of the magnetic topological insulator layers, resembling a high Chern number QAH insulator. The QAH multilayers provide an excellent platform to study various topological states of matter. 相似文献
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转眼本命年就要来了。羊年的春节格外的晚,晚得叫人有些手足无措,却也顺理成章。在人们大谈星际穿越,时钟变慢这些时下最为流行的"物理"之时,在大街小巷间耄耋黄发高谈阔论天地间格物致知的玄机背后:殊不觉得公历和农历,就像人和他的影子般静静地陪伴在我们左右,日复一日,将虚虚实实的我们虚虚实实地困在两位老祖宗划出来的两个时空之间。在元旦与春节间,在无数的聚会、祈福与期盼间,我们赫然发现,也许我 相似文献
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研究焦磷酸盐溶液中,铜电沉积过程的机理是电化学中的一个老问题。在过去,对于这个电极过程的认识是众说纷云的。有人认为控制阴极过程速度的是物质传递;也有人认为是迟缓放电,或是电极阴极钝化。近年来对于电极过程动力学的某些概念有了更深 相似文献
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Oxygen vacancies play a crucial role in determining the catalytic properties of Ce-based catalysts, especially in oxidation reactions. The design of catalytic activity requires keen insight into oxygen vacancy formation mechanisms. In this work, we investigate the origin of oxygen vacancies in CeO2 from the perspective of electron density {via} high-energy synchrotron powder x-ray diffraction. Multipole refinement results indicate that there is no obvious hybridization between bonded Ce and O atoms in CeO2. Subsequent quantitative topological analysis of the experimental total electron density reveals the closed-shell interaction behavior of the Ce—O bond. The results of first-principles calculation indicate that the oxygen vacancy formation energy of CeO2 is the lowest among three commonly used redox catalysts. These findings indicate the relatively weak bond strength of the Ce—O bond, which induces a low oxygen vacancy formation energy for CeO2 and thus promotes CeO2 as a superior catalyst for oxidation reactions. This work provides a new direction for design of functional metal oxides with high oxygen vacancy concentrations. 相似文献