Dielectric-barrier discharge (DBD) is a typical non-equilibrium gas discharge with AC at low temperature and atmospheric pressure.In this paper the influence of DBD plasma on the crystallization of Cu(NO3)2· 3H2O is investigated.The experimental results show that DBD plasma has great influence on inducing the primary nucleation thus greatly reducing the nucleation time.Moreover,by applying DBD plasma,the morphology of Cu(NO3)2·3H2O was controlled during crystallization.In crystallization without DBD treatment,quadrilateral Cu(NO3)2·3H2O crystals were preferentially produced.However,if DBD plasma was applied during the nucleation process,the typical quadrilateral forms of crystal seeds transform to hexagonal crystals.The hexagonal crystals can grow to either hexagonal prism without further DBD plasma treatment or unique contact-twinned shaped hexangular star form under the environment of DBD plasma.
Most current catalyst preparation methods cause pollution to air, water and land with the use of hazardous chemicals, lengthy operation time, high energy input and excessive water usage. The development of green catalyst preparation is necessary to prevent and eliminate waste from each step of the catalyst preparation. We summarize recent progress in the application of cold plasmas for green catalyst preparation. Cold plasma preparation can reduce the catalyst size, improve the dispersion and enhance catalyst-support interaction with the use of less or no hazardous chemicals. These improvements also lead to the enhancement of catalyst activity and stability. An alternative room temperature electron reduction with a non-hydrogen plasma as an electron source was developed for the reduction of noble metal ions in which no hazardous chemical reducing agent or hydrogen was needed. This creates many opportunities for the development of supported catalysts with heat sensitive substrates, including metal organic frameworks （MOFs）, covalent organic framework（COFs）, high surface area carbon, peptide, DNA, proteins and others. A novel floating metal catalyst on a water（or solution） surface has been established. Template removal using low temperature cold plasmas also leads to the formation of high surface area porous materials with characteristics that are normally only obtainable with high temperature calcination, but sintering can be avoided. Micro combustion has been developed for the removal of carbon template using cold plasma. This is promising for preparing many structured oxides in a simple way with no use of auxiliary chemicals. Many opportunities exist for the use of cold plasmas to make multi-metallic oxides. Some future development ideas are addressed.
The effect of the reduction method on the catalytic properties of palladium catalysts supported on activated carbon for the oxidation of D-glucose was examined.The reduction methods investigated include argon glow discharge plasma reduction at room temperature,reduction by flowing hydrogen at elevated temperature,and reduction by formaldehyde at room temperature.The plasma-reduced catalyst shows the smallest metal particles with a narrow size distribution that leads to a much higher activity.The catalyst characteristics show that the plasma reduction increases the amount of oxygen-containing functional groups,which significantly enhances the hydrophilic property of the activated carbon and improves the dispersion of the metal.
