In-situ reduction of silver by surface DBD plasma:a novel method for preparing highly effective electromagnetic interference shielding Ag/PET

Electromagnetic interference(EMI)shielding composites with good flexibility and weatherability properties have attracted increased attention.In this study,we combined the surface modification method of sub-atmospheric pressure glow discharge plasma with in situ atmospheric pressure surface dielectric barrier discharge plasma(APSDBD)reduction to prepare polyethylene terephthalate supported silver(Ag/PET).Due to the prominent surface modification of PET film,mild plasma reduction,and effective control of the silver morphology by polyvinylpyrrolidone(PVP),a 3.32μm thick silver film with ultralow sliver loading(0.022 wt%)exhibited an EMI shielding efficiency(SE)of 39.45 d B at 0.01 GHz and 31.56 d B at 1.0 GHz(>30 d B in the range of 0.01–1.0 GHz).The SEM results and EMI shielding analysis indicated that the high performance originated from the synergistic effect of the formation of silver nanoparticles(Ag NPs)with preferentially oriented cell-like surface morphologies and layer-by-layer-like superimposed microstructures inside,which demonstrated strong microwave reflection properties.Fourier transform infrared spectrometer and x-ray diffractometer showed that the surface structures of the heat-sensitive substrate materials were not destroyed by plasma.Additionally,APSDBD technology for preparing Ag/PET had no special requirements on the thickness,dielectric constant,and conductivity of the substrate,which provides an effective strategy for manufacturing metal or alloy films on surfaces of heat-sensitive materials at a relatively low cost.

Plasma-assisted Ru/Zr-MOF catalyst for hydrogenation of CO2 to methane

As an important type of metal-organic framework(MOF),Zr-MOF shows excellent CO2 adsorption performance.In this work,a Zr-MOF was synthesized by a solvothennal method and adopted to support Ru through simple incipient-wetness impreg nation.Then the Ru/Zr-MOF was applied for CO2 hydrogenation(Vh2:VCO2=4:1)with the assistance of dielectric banner dischai'ge(DBD)plasma.The hydrogenation of Cd2 results showed that methane was produced selectively under the synergistic effect between plasma and the Ru/Zr-MOF catalyst,and the selectivity and yield of methane reached 94.6%and 39.1%,respectively.The XRD and SEM analyses indicate that the basic crystalline phase structure and morphology of the Zr-MOF and Ru/Zr-MOF remained the same after DBD plasma treatment,suggesting that the catalysts are stable in plasma.The guest molecules in the pores of the Zr-MOF are removed and the Ru"ions are reduced to metallic Ru()in the reduction atmosphere according to the BET and XPS results,which are responsible for the high performance of plasma with the Ru/Zr-MOF catalyst.In situ optical emission spectra of pure plasma,plasma with Zr-MOF,and plasma with Ru/Zr-MOF were measured,and the active species of C,H and CH for CO2 hydrogenation were detected.The plasma-assisted Ru/Zr-MOF exhibited high catalytic activity and stability in CO2 hydrogenation to methane,and it has great guiding significance for CO2 hydrogenation by using plasma and MOF materials.

Partially crystallized Pd nanoparticles decorated TiO_2 prepared by atmospheric-pressure cold plasma and its enhanced photocatalytic performance

TiO2 decorated with partially crystallized Pd nanoparticles （Pd/TiO2-P） was successfully prepared by atmospheric-pressure dielectric barrier discharge cold plasma. The XRD and XPS analyses proved that Pd ions were reduced to partially crystallized metallic Pd nanoparticles in Pd/TiO2-P. The XPS spectra also indicated that an enhanced metal-support interaction was formed due to the existence of partially crystallized Pd nanoparticles with lower coordination number in Pd/TiO2-P. Photocatalytic activity of Pd/TiO2-P was much higher than that of TiO2 samples decorated with well crystallized Pd nanoparticles.

Methane conversion under cold plasma over Pd-containing ionic liquids immobilized on γ-Al_2O_3

Pd-containing ionic liquid （IL） 1-hexyl-3-methylimidazolium tetrafluoroborate （C6MIMBF4） immobilized on γ-Al2O3 （Pd-IL/γ-Al2O3） was prepared and characterized by Fourier transform infrared spectroscopy （FTIR）, scanning electron microscopy （SEM） and Brunauer-Emmett- Teller （BET） analysis. The influences of C6MIMBF4 loading and Pd on methane conversion to C2 hydrocarbons under cold plasma were investigated. FTIR and SEM analyses indicated that C6MIMBF4 had been successfully immobilized on γ-Al2O3 and the C6MIMBF4 showed excellent stability under cold plasma. The results of BET and methane conversion showed that with the increase in immobilization amount of C6MIMBF4 onto γ-Al2O3, the specific surface area and pore volume of IL/γ-Al2O3 decreased, while the selectivity and yield of C2 hydrocarbons increased. The selectivity of C2 hydrocarbons was 94.6% when the loading of C6MIMBF4 was 40%, and the percentage of C2H4 in C2 hydrocarbons was as high as 64% when using Pd-IL/γ-Al2O3 as a catalyst with no conventional thermal reduction treatment. Optical emission spectra （OES） from the cold plasma reactor during methane conversion were also studied. The results indicated that the intensity of the C2, CH, H, and C active species from methane and hydrogen decomposition increased when IL/γ-Al2O3 or Pd-IL/γ-Al2O3 was introduced into the plasma system. Based on the analyses of the gas product and OES spectra, it can be concluded that the surface catalyzed reactions between plasma and ionic liquid were very important for the reduction of Pd2＋ and the formation of C2H4.

Plasma-assisted Co/Zr-metal organic framework catalysis of CO_(2)hydrogenation:influence of Co precursors

In this study,Co/Zr-metal organic framework(MOF)precursors were obtained by a roomtemperature liquid-phase precipitation method and the equivalent-volume impregnation method,respectively,using a Zr-MOF as the support,and Co/Zr-MOF-M and Co/Zr-MOF-N catalysts were prepared after calcination in a hydrogen-argon mixture gases(VAr:V_(H_(2))=9:1)at 350℃for 2 h.The catalytic activities of the prepared samples for CO_(2)methanation under atmosphericpressure cold plasma were studied.The results showed that Co/Zr-MOF-M had a good synergistic effect with cold plasma.At a discharge power of 13.0 W,V_(H_(2)):VCO_(2)=4:1 and a gas flow rate of 30 ml·min^(-1),the CO_(2)conversion was 58.9%and the CH4 selectivity reached 94.7%,which was higher than for Co/Zr-MOF-N under plasma(CO_(2)conversion 24.8%,CH4 selectivity 9.8%).X-ray diffraction,scanning electron microscopy,transmission electron microscopy,N_(2)adsorption and desorption(Brunauer-Emmett-Teller)and x-ray photoelectron spectroscopy analysis results showed that Co/Zr-MOF-M and Co/Zr-MOF-N retained a good Zr-MOF framework structure,and the Co oxide was uniformly dispersed on the surface of the Zr-MOF.Compared with Co/Zr-MOF-N,the Co/Zr-MOF-M catalyst has a larger specific surface area and higher Co^(2+)/Cototaland Co/Zr ratios.Additionally,the Co oxide in Co/ZrMOF-M is distributed on the surface of the Zr-MOF in the form of porous particles,which may be the main reason why the catalytic activity of Co/Zr-MOF-M is higher than that of Co/ZrMOF-N.