| This paper focuses on a systematic study of the mechanism and synergetic catalytic properties of carbon nanotubes (CNTs) based and graphene based metal and metal oxide catalysts. Detailed characterization, catalytic reaction experiments, molecular dynamics (MD) simulations and density functional theory (DFT) calculations were performed to reveal the mechanism and evaluate synergistic catalytic performance of above.Carbon nanotube-supported CuO nanoparticle catalyst (CuO/CNTs) was prepared, and the catalytic property of CuO/CNTs was investigated. XRD, TEM, and TG were used to characterize the structural properties of the prepared CuO/CNTs system. CuO/CNTs catalyzed ozonation showed 60% higher removal rate than that of ozonation alone without CuO/CNTs. Through the study of electron paramagnetic resonance tests, it was found that high concentration of·OH was generated during CuO/CNTs catalyzed ozonation and degradation reaction of rhodamine B followed a radical oxidation mechanism. DFT calculations showed that p orbital of C atoms in the outer wall of CNTs hybridized with the d orbital of Cu atoms, electrons transferred from carbon nanotube, which is electron-rich CuO/CNTs interface, facilitating the decomposition of ozone molecules and the generation of hydroxyl radicals during reactions. Interfacial electron transfer is non-linear, which verified the synergetic effect of CNTs as revealed by the electric field regulation experiments.CuO nanoparticles were encapsulated into CNTs to prepare carbon nanotube-filled CuO catalyst (CuO@CNTs), the catalytic propertiy of which was also investigated. XRD, TEM and TG was used to characterize the structure of CuO@CNTs, which showed that CuO particles are dispersed on the inside wall of carbon nanotube. CuO@CNTs showed a removal rate of about 8% higher than that of CuO/CNTs. The catalytic activity of CuO@CNTs is stable. Through the study of electron paramagnetic resonance, it was found that high concentration of·OH could be generated during CuO@CNTs catalyzed ozonation than with CuO/CNTs, and the degradation reaction followed a radical oxidation mechanism. DFT calculations showed that p-d hybridization occurs between the C atoms and Cu atoms of the CuO@CNTs composite. Due to the confinement effect, ionic bond of CuO delocalized, leading to extended valence band structure and higher migration of charge carriers, promoting the catalytic reactions. Studying the modulation effect of external electric field under different intensities on the electron transfer in the catalytic reaction, revealed that CNTs have a synergetic effect on the catalytic properties of CuO. It was found that carbon nanotubes can shield the external electric field to sustain the catalytic reation in the tube up to higher electric field intensity range that would not lead to the breakdown of carbon nanotube. This shielding effect of carbon nanotubes can be imployed to achieve confinded reaction complex environments.Graphene-supported Pt nanoparticles catalyst (Pt/graphene) was prepared and used for degradation of 2,4-dichlorophenol to investigate its catalytic property. Pt/graphene was characterized by XRD, TEM, RS, and AFM, which shows that Pt nanoparticles dispersed on graphene. With Pt/graphene catalyzed ozonation the removal rate is about 65% higher than with ozonation alone. DFT calculations showed the interaction between Pt and graphene, and the quantum-trapping effect enable faster electron transfer throught phases, leading to superious catalytic effect. The regulation effect of external electric field on Pt/graphene system further verified that synergetic electronic interaction between graphene and Pt played an essential role for the synergetic effect on catalytic behavior of Pt.Leucine and DNA molecules were used to functionalize graphene. Leucine molecules self-assembled on graphene and formed two-dimensional stable hydrogen bond network with a binding energy of ?0.31eV. The adsorpted leucine changed the local electronic properties of graphene. ssDNA extend fully on graphene with a stableπ-πstacking with the binding energy of–15.810eV. Functionalizing graphene with different biological molecules produces graphene based Pt particles. The transfer direction of electrons through interface was reversed and the electronic properties and redox of the functionalized graphene-based Pt nanoparticles catalyst was modified, regulating the catalytic selectivity and activity the catalyst. For Leucine-functionalized Pt/graphene catalyst, the energy barrier forα-dehydrogenation of ethanol is 0.433eV, which is lower than that of Pt/graphene (0.518eV). In comparison, ssDNA-functionalized Pt/graphene catalyst showed higher energy barrier of 0.853eV. |
