A Study Of Electroless Plating In Pd Composite Membrane Preparation And Graphite Electrode Modification

Energy and environmental issues are the common concerns around the world. In asense, the development of human society is indispensible from the emergence ofhigh-quality energy and the use of advanced energy technologies. The production,purification and storage technologies of hydrogen become a research hotspot sincebased on H2a clean and high efficient energy system can be built. Palladiumcomposite membrane has been extensively studied for hydrogen purification and inthe preparation of the membrane reactor because of its high hydrogen permeationselectivity, good mechanical and thermal stability and catalytic activity. In addition,with the development and utilization of new energies such as solar and wind energy,new challenges are arison for energy storage. All vanadium redox flow battery is anefficient and green secondary battery which is most likely to partially replace thewidely used but low efficient lead-acid batteries.A dense and stable Pd membrane for hydrogen separation and purification wereprepared with a modified electroless plating method with ultrasound condition. Thehydrogen permeability was tested. A porous stainless steel was used as the carrier andin-situ oxidized and sol-gel CeO2were used as the intermediate layer for moderatinginterdiffusion of the metal atoms. The results showed that using both the in-situoxidized and CeO2as the intermediate layers can effectively modified the surface ofthe porous stainless steel; the palladium membrane prepared with ultrasonic conditionwas more compact and dense. Smaller Pd particle size was formed which is morefavourable to the formation of the dense and ultra-thin palladium compositemembranes. Permeation results showed that the prepared palladium membrane has ahigh permeation rate with a high selectivity. The thickness of the prepared memrane isabout8μm with a good air tightness. The H2permeation flux of Pd/CeO2-PSS isabout1.2mol/(m2·s) and Pd/in-situ oxidized-PSS is about0.16mol/(m2·s) at400oCand0.1Mpa. The main resistance of the composite membrane during H2permeationexisted in the support layer rather than in the thin Pd membrane.The modification of the graphite electrodes with Pd and Ag improved theelectrochemical activity and lowered the cost when used in vanadium redox flow battery. However, Cu modified electrode is not suitable for this system. The metalswere deposited with an electroless plating method. An ionic liquid(Tetraethylammonium hexafluorophosphate amines, TEAPF6) was used as thesupporting electrolyte. Acetylacetone vanadium was used as the active substance, andacetonitrile as the solvent. Cyclic voltammetry were tested under anhydrous anaerobicconditions. The electrode kinetics study shows that the V(Ⅱ)/V(Ⅲ) and V(Ⅲ)/V(Ⅳ)redox reaction are subjected to irreversible reactions, the diffusion coefficient ofacetylacetone vanadium is about1.21×10-6cm2/s at room temperature, and theelectrode reactions are diffusion controlled.The graphite electrodes are also treated with heating at200-400oC to furtherimprove the electrochemical activity. When treated at400oC, the electrochemicalactivity improved to a certain extent. However, when the temperature is higher than600oC, the electrochemical activity decreased due to the excessive oxidation of thereactive functional groups.