Chen Tzu-Ning, Kao Jui-Cheng, Zhong Xin-Yan, Chan Shang-Ju, Patra Anindya S, Lo Yu-Chieh, Huang Michael H
Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan.
Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan.
ACS Cent Sci. 2020 Jun 24;6(6):984-994. doi: 10.1021/acscentsci.0c00367. Epub 2020 Jun 4.
CuO 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 CuO cubes showed surprisingly high activity toward methyl orange photodegradation after 4-EA modification, while the already active CuO 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 CuO cubes. Electrochemical impedance spectroscopy also indicates reduced charge transfer resistance of the functionalized CuO crystals. A band diagram constructed from UV-vis spectral and Mott-Schottky measurements reveals significant band energy shifts in all CuO 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 CuO, 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 CuO cubes photocatalytically active. Proper molecular decoration represents a powerful approach to improving the photocatalytic efficiency of semiconductors.
用共轭的4-乙炔基苯胺（4-EA）对菱形十二面体、八面体和立方体的氧化铜进行了密集修饰，以考察其晶面依赖性光催化活性。红外光谱证实了4-EA的炔基与表面铜原子的键合。光催化惰性的氧化铜立方体在4-EA修饰后对甲基橙光降解表现出惊人的高活性，而原本就具有活性的菱形十二面体和八面体氧化铜的光催化活性增强。电子、空穴和自由基清除剂实验证明，在功能化的氧化铜立方体中发生了光催化电荷传输过程。电化学阻抗谱也表明功能化的氧化铜晶体的电荷转移电阻降低。由紫外可见光谱和莫特-肖特基测量构建的能带图显示，用4-EA修饰后，所有氧化铜样品的能带能量都有显著变化。通过密度泛函理论（DFT）计算，在氧化铜的带隙内，价带最大值上方略微出现了一个新的能带，通过能带分解电荷密度分析发现它起源于4-EA。4-EA分子上增加的电荷密度以及到达4-EA产生的能带的最小电子跃迁能量是使{100}面结合的氧化铜立方体具有光催化活性的因素。适当的分子修饰是提高半导体光催化效率的有效方法。
