新型二元贵金属氮化物的合成与表征

新型二元贵金属族氮化物在硬度和电学方面表现出优异的性能,被视为一种潜在的超硬功能材料.但由于其难以达到的高温高压合成条件,使得人们很难对其晶体结构、热力学规律和物化性质等方面进行更为深入的研究.因此,探寻一种在较低温压条件下制备贵金属氮化物的途径成为材料制备领域的焦点.本研究从制备碳包覆贵金属钯(Pd)超细纳米颗粒前驱体为出发点,采用直流电弧法与激光加温金刚石对顶砧相结合的方法,在7 G Pa压力和800 K温度的条件下成功制备氮化钯(PdN 2)纳米颗粒,这一合成条件较之前传统方法大幅降低,对其工业化批量生产的成本降低具有重要意义.本研究开创性的将纳米与高温高压相结合,首次制备了贵金属氮化物纳米级材料,为此类氮化物的合成提供了新途径,为其他潜在超硬材料的制备提供了新思路.

Nitrogen ligands in two-dimensional covalent organic frameworks for metal catalysis

We introduced bipyridine ligands into a series of two‐dimensional （2D） covalent organic frame‐works （COFs） using 2,2’‐bipyridine‐5,5’‐dicarbaldehyde （2,2’‐BPyDCA） as a component in the mixed building blocks. The framework of the COFs was formed by the linkage of imine groups. The ligand content in the COFs was synthetically tuned by the content of 2,2’‐BPyDCA, and thus the amount of metal, palladium（II） acetate, bonded to the nitrogen ligands could be manipulated. Both the bipyri‐dine ligands and imine groups can coordinate with Pd（II） ions, but the loading position can be var‐ied, with one ligand favoring binding in the space between adjacent COFs’ layers and the other lig‐and favoring binding within the pores of the COFs. The Pd（II）‐loaded COFs exhibited good catalytic activity for the Heck reaction.

Palladium nanoparticles assembled on titanium nitride for enhanced electrochemical hydrodechlorination of 2,4-dichlorophenol in water

We report a one‐pot surfactant‐free wet‐chemical reduction approach to the synthesis of palladium/titanium nitride(Pd/TiN)and Pd/carbon(Pd/C)composites,in which^5 nm Pd NPs were uniformly dispersed on TiN or C.In terms of catalytic performance,Pd/TiN showed enhanced efficiency and stability compared with those of Pd/C and bare TiN in the electrocatalytic hydrodechlorination(EHDC)reaction of 2,4‐dichlorophenol(2,4‐DCP)in aqueous solution.The superior performance of Pd/TiN arises from the promotion effect of TiN.Strong metal‐support interactions modified the electronic structure of Pd,which optimized generation of H*ads and 2,4‐DCP adsorption/activation.The cathode potential plays a vital role in controlling the EHDC efficiency and the product distribution.A working potential of?0.80 V was shown to be optimal for achieving the highest EHDC efficiency and maximizing conversion of 2,4‐DCP to phenol(P).Our studies of the reaction pathway show that EHDC of 2,4‐DCP on Pd/TiN proceeded by 2,4‐DCP→p‐chlorophenol(p‐CP),o‐chlorophenol(o‐CP)→P;however,Pd/TiN presented little selectivity for cleavage of p‐C‐Cl vs o‐C‐Cl.This work presents a new approach to enhancing Pd performance towards EHDC through the effects of a support.The strategy demonstrated here could also be extended to design highly efficient catalysts for other hydrogenation reactions.

Synthesis and Crystal Structure of Pd(AETYF)Cl_2CH_2Cl_2 [AETYF = 4'5'Diaza-9' (4,5-bis(ethylthio)-1,3-dithiole-2-ylidene)-fluorene]

A stable Pd(II) compound Pd(AETYF)Cl2CH2Cl2 (AETYF = 4?5?diaza-9? (4,5-bis(ethylthio)-1,3-dithiole-2-ylidene)-fluorene) has been synthesized and its crystal structure was determined by X-ray crystallography. The crystal is of monoclinic, space group P21/c with a = 15.249(6), b = 8.619(3), c = 19.078(7) ? b = 106.932(8), C19H18Cl4N2PdS4, Mr = 650.79, V = 2398.6(16) 3, Z = 4, Dc = 1.802 g/cm3, F(000) = 1296, m = 1.579 mm-1, Npar = 268, the final R = 0.0538 and wR = 0.1282 for 5068 observed reflections with I > 2s(I). The crystal structure determi- nation shows that the atoms of the molecule, except two ethyl-groups, are conjugated in a quasi- plane and these molecules are further stacked or contacted via plane to plane or edge to edge p-p interactions, forming parallel molecular chains along the b axis.

Pd-M-TiO_(2)(M=Mn,Cu,Ce and Fe)as passive NO_(x) adsorber(PNA)at low temperature

A series of transition metal Mn,Cu,Ce and Fe were loaded on TiO_(2) by sol-gel method with noble metal Pd as promotor for the application of passive NO_(x) absorber.Experiments on adsorption and desorption of NO_(x) were conducted and characterization methods such as X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM)and in situ Fourier transform infrared spectroscopy(in situ DRIFTS)were involved.The experimental results show that Mn-contained catalysts,Mn-Ti and Pd-Mn-Ti,performed excellent NO_(x) adsorbing ability and appropriate desorption temperature window.On the other hand,Ce-and Cu-contained samples were not suitable for the purpose of PNA.In addition to the low adsorption capacity,these two series of catalysts released massive amount of NO below 150℃.Characterization results indicated that Pd was highly dispersed on all catalysts.The loading of Pd lowered not only the valence states of transition metals but surface oxygen percentage as well.From in situ DRIFTS tests,the Pd had little influence on the types of adsorbed substances for Mn,Ce and Cu series.However,the storage forms of NO_(x) were obviously different on Pd-Fe-Ti and Fe-Ti.

STUDIES ON THE CATALYTIC REACTION OF NITROGEN OXIDE ON METAL MODIFIED ACTIVATED CARBON FIBERS

The catalytic reaction of NO with CO and decomposition of NO over metal modified ACFs were investigated and compared with other carriers supported catalysts. It is demonstrated that Pd/ACF and Pd/Cu/ACF have high catalytic activity for the reaction of NO/CO, while Pt/ACF, Pt/Cu/ACF and Co/Cu/ACF have very low catalytic activity in similar circumstance. Pd-modified ACF possesses high catalytic decomposition of NO at 300℃. Pd/CB and Pd/GAC present good catalytic decomposition ability for NO only at low flowrate. Pd/G, Pd/ZMS and Pd/A however, do not show any catalytic activity for NO decomposition even at 400℃. Catalytic temperature, NO flowrate and loading of metal components affect the decomposition rate of NO. The coexistence of Cu with Pd on Cu/Pd/ACF leads to crystalline of palladium to more unperfected so as to that increase the catalytic activity.

Palladium-catalyzed intermolecular C–H amidation of indoles with sulfonyl azides

A new kind of intermolecular indole C–H amidation reaction catalyzed by the most frequently used palladium catalyst has been developed.Sulfonyl azide was employed as an innovative nitrogen source and environmentally benign nitrogen was produced as the only byproduct.