Three-dimensional （3D） hierarchical Pt-Cu tetragonal, highly branched, and dendritic superstructures have been synthesized by a facile template-free hydrothermal approach, showing growth patterns along （111, 110）, （111）, and （100） planes, respectively. These structures have been characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）, energy dispersive X-ray spectroscopy （EDX）, inductively coupled plasma optical emission spectrometry （ICP-OES） and a detailed formation mechanism has been developed, which shows that the in situ formed 12 and the galvanic replacement reaction between Cu and Pt4, may guide the formation of these superstructures. The comparative electrocatalytic properties have been investigated for methanol and ethanol oxidation. Due to their interconnected arms, sufficient absorption sites, and exposed surfaces, these superstructures exhibit enhanced electrocatalytic performance for electro-oxidation of methanol and ethanol when compared with commercial Pt/C and Pt black.
Farhat Nosheen Zhicheng Zhang Guolei Xiang Biao Xu Yong Yang Faisal Saleem Xiaobin Xu Jingchao Zhang Xun Wang
Low-temperature CO oxidation has attracted extensive interest in heterogeneous catalysis because of the potential applications in fuel cells,air cleaning,and automotive emission reduction.In the present study,theoretical investigations have been performed using density functional theory to elucidate the crystal plane effect and structure sensitivity of Co3O4 nano-catalysts toward catalyzing CO oxidation.It is shown that the surface Co–O ion pairs are the active site for CO oxidation on the Co3O4 surface.Because of stronger CO adsorption and easier removal of lattice oxygen ions,the Co3O4（011）surface is shown to be more reactive for CO oxidation than the Co3O4（001）surface,which is consistent with previous experimental results.By comparing the reaction pathways at different sites on each surface,we have further elucidated the nature of the crystal plane effect on Co3O4 surfaces and attributed the reactivity to the surface reducibility.Our results suggest that CO oxidation catalyzed by Co3O4 nanocrystals has a strong crystal plane effect and structure sensitivity.Lowering the vacancy formation energy of the oxide surface is key for high CO oxidation reactivity.
A simple method to fabricate Mo-based nanostructures were developed by the thermal decomposition of Mo Ox-based organic–inorganic hybrid nanowires. Well-defined Mo-based nanostructures, including Mo O2 and Mo O3 nanowires, can be prepared by changing the hybrid precursor. More importantly, Mo2C/Mo O2 heterostructures with porous structure were successfully synthesized under an inert atmosphere. The resultant Mo2C/ Mo O2 heterostructures show enhanced electrocatalytic activity and superior stability for electrochemical hydrogen evolution from water. The enhanced performance might be ascribed to the high electrical conductivity and porous structures with one-dimensional structure. Indeed, our result described here provides a new way to synthesize other Mo-based nanostructures for various applications.
Metal-semiconductor nanoheterostructure(NHS) exhibits fascinating catalytic performance due to the strong metal-support interaction(SMSI). SMSI in liquid-solid heterogeneous catalysis based on NHS was rarely investigated as compared to the gas-solid counterpart. Two issues, namely, the wet-chemical preparation of monodisperse model catalyst and in-situ characterization on the electronic structure, are challenging and studied here. The size of the metal catalyst was finely tuned in a Pd-Fe2O3 NHS and electrochemical test revealed that the electronic states differ significantly in liquid environment from in vacuum. The combined amendments resulted in a more reliable conclusion on the SMSI in Suzuki coupling. This study might give some clues on the illusive in-liquid structure-property relationships.
A novel one-pot approach to synthesize the tiara-like Pd(II) thiolate complex compound, [Pd(SCH_3)_2]_6, was developed. In this strategy, dimethyl sulfoxide(DMSO) was used as a thiolate source instead of methyl mercaptan(CH_3SH). DMSO was first decomposed into CH_3SH and formaldehyde(HCHO); then, the in situ as-formed CH_3SH molecules reacted with palladium acetate, and formed [Pd(SCH_3)_2]_6. By tuning the reaction condition, the morphology of the [Pd(SCH_3)_2]_6 assemblies can change from microprism to nanosphere. The characterization of the pyrolysis product demonstrated that these two kinds of [Pd(SCH_3)_2]_6 assemblies with different shapes could further decompose into palladium or palladium sulfides through different pyrolysis conditions.
In this work, ultra-large sheet NiAl-layered double hydroxide(LDH)/reduced graphene oxide(RGO) nanocomposites were facilely synthesized via in situ growth of NiAl-LDH on a graphene surface without any surfactant or template. It was found that with a microwave-assisted method, NiAl-LDH nanosheets grew evenly on the surface of graphene. With this method, the formation of NiAl-LDH and reduction of graphene oxide were achieved in one step. The unique structure endows the electrode materials with a higher specific surface area, which is favorable for enhancing the capacity performance. The morphology and microstructure of the as-prepared composites were characterized by X-ray diffraction, Brunauer-EmmettTeller surface area measurement, and transmission electron microscopy. The specific surface area and pore volume of the RGO/LDH composite are 108.3 m^2 g^(-1) and 0.74 cm^3 g^(-1), respectively, which are much larger than those of pure LDHs(19.8 m^2 g^(-1) and 0.065 cm^3 g(-1), respectively). The capacitive properties of the synthesized electrodes were studied using cyclic voltammetry and electrochemical impedance spectroscopy in a three-electrode experimental setup. The specific capacitance of RGO/LDHs was calculated to be 1055 F g^(-1) at 1 Ag^(-1). It could be anticipated that the synthesized electrodes will find promising applications as novel electrode materials in supercapacitors and other devices because of their outstanding characteristics of controllable capacitance and facile synthesis.
