Cu₂O rhombic dodecahedra, octahedra, and cubes were densely modified with conjugated 4-ethynylaniline (4-EA) for facet-dependent photocatalytic activity examination. Infrared spectroscopy affirms bonding of the acetylenic group of 4-EA onto the surface copper atoms. The photocatalytically inactive Cu₂O cubes showed surprisingly high activity toward methyl orange photodegradation after 4-EA modification, while the already active Cu₂O rhombic dodecahedra and octahedra exhibited a photocatalytic activity enhancement. Electron, hole, and radical scavenger experiments prove that the photocatalytic charge transport processes have occurred in the functionalized Cu₂O cubes. Electrochemical impedance spectroscopy also indicates reduced charge transfer resistance of the functionalized Cu₂O crystals. A band diagram constructed from UV–vis spectral and Mott–Schottky measurements reveals significant band energy shifts in all Cu₂O samples after decorating with 4-EA. From density functional theory (DFT) calculations, a new band has emerged slightly above the valence band maximum within the band gap of Cu₂O, which has been found to originate from 4-EA through band-decomposed charge density analysis. The increased charge density localized on the 4-EA molecule and the smallest electron transition energy to reach the 4-EA-generated band are factors making {100}-bound Cu₂O cubes photocatalytically active. Proper molecular decoration represents a powerful approach to improving the photocatalytic efficiency of semiconductors.

中文翻译：

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带状结构调整导致4-乙炔基苯胺官能化的Cu2O多面体的特定方面光催化活性增强。

Cu ₂ O菱形十二面体，八面体和立方体用共轭4-乙炔基苯胺（4-EA）进行了密集修饰，以检测方面相关的光催化活性。红外光谱证实4-EA的炔基键合到表面铜原子上。在4-EA修饰后，无光催化活性的Cu ₂ O立方体显示出对甲基橙光降解的惊人高活性，而已经具有活性的Cu ₂ O菱形十二面体和八面体表现出光催化活性增强。电子，空穴和自由基清除剂实验证明，在功能化的Cu _2中发生了光催化电荷传输过程O多维数据集。电化学阻抗谱还表明功能化的Cu ₂ O晶体的电荷转移电阻降低。由UV-vis光谱和Mott-Schottky测量构建的能带图显示，用4-EA修饰后，所有Cu ₂ O样品中的能带均发生了明显的位移。根据密度泛函理论（DFT）的计算，在Cu ₂ O的带隙内，在价带最大值上方出现了一个新的能带，该带隙是通过带分解电荷密度分析从4-EA发现的。位于4-EA分子上的增加的电荷密度和达到4-EA生成的能带的最小电子跃迁能是造成{100}结合Cu _2的因素O立方体具有光催化活性。正确的分子修饰是改善半导体光催化效率的有力方法。