Zheng Kai, Wu Yang, Zhu Juncheng, Wu Mingyu, Jiao Xingchen, Li Li, Wang Shumin, Fan Minghui, Hu Jun, Yan Wensheng, Zhu Junfa, Sun Yongfu, Xie Yi
Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China.
National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China.
J Am Chem Soc. 2022 Jul 13;144(27):12357-12366. doi: 10.1021/jacs.2c03866. Epub 2022 Jun 28.
The huge challenge for CH photooxidation into CHOH lies in the activation of the inert C-H bond and the inhibition of CHOH overoxidation. Herein, we design two-dimensional in-plane -scheme heterostructures composed of two different metal oxides, with efforts to polarize the symmetrical CH molecules and strengthen the O-H bond in CHOH. As a prototype, we first fabricate ZnO/FeO porous nanosheets, where high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy affirm their in-plane -scheme heterostructure. Fourier transform infrared spectra and electron paramagnetic resonance spectra demonstrate their higher amount of ·CH radicals relative to the pristine ZnO porous nanosheets, in which density functional theory calculations validate that the high local charge accumulation on Fe sites lowers the CH adsorption energy from 0.14 to 0.06 eV. Moreover, the charge-accumulated Fe sites strengthen the polarity of the O-H bond in CHOH through transferring electrons to the O atoms, confirmed by the increased barrier from 0.30 to 2.63 eV for *CHO formation, which inhibits the homolytic O-H bond cleavage and thus suppresses CHOH overoxidation. Accordingly, the CHOH selectivity over ZnO/FeO porous nanosheets reaches up to nearly 100% with an activity of 178.3 μmol g, outperforming previously reported photocatalysts without adding any oxidants under room temperature and ambient pressure.
将CH光氧化为CHOH面临的巨大挑战在于惰性C-H键的活化以及CHOH过度氧化的抑制。在此，我们设计了由两种不同金属氧化物组成的二维面内异质结构，致力于使对称的CH分子极化并增强CHOH中的O-H键。作为原型，我们首先制备了ZnO/FeO多孔纳米片，高分辨率透射电子显微镜和X射线光电子能谱证实了它们的面内异质结构。傅里叶变换红外光谱和电子顺磁共振光谱表明，相对于原始的ZnO多孔纳米片，它们具有更高含量的·CH自由基，其中密度泛函理论计算验证了Fe位点上高的局部电荷积累将CH吸附能从0.14 eV降低到0.06 eV。此外，电荷积累的Fe位点通过将电子转移到O原子上增强了CHOH中O-H键的极性，这通过*CHO形成的势垒从0.30 eV增加到2.63 eV得到证实，这抑制了O-H键的均裂，从而抑制了CHOH的过度氧化。因此，ZnO/FeO多孔纳米片上的CHOH选择性高达近100%，活性为178.3 μmol g，在室温常压下不添加任何氧化剂的情况下性能优于先前报道的光催化剂。
