Rearch On The Electrodeposition Of Molybdenum In [BMP]Tf₂N Ionic Liquid And Its Mechanism

Molybdenum is applied extensively for its excellent performance of high wear resistance and high heat resistance.It has unique status in the field of national defense and modern electronic information.Traditional methods for preparing Mo coating have the disadvantages of the high temperature and the degradation of substrates mechanics performance.Ionic liquid is an new tape of low temperature and green solvent.Theory and application of ionic liquid in electrochemistry is a hot area of research in material and surface engineering field.For the sake of preparing Mo coating in low temperature,carrying out the rearch on the electrodeposition of molybdenum in the ionic liquid and its mechanism has significant engineering application value and theoretic meaning.Electrodeposition of molybdenum in the 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide([BMP]Tf2N)ionic liquid was investigated.MoCl5 and MoCl3 were used for Mo source,and reduction behavior and mechanism of molybdenum in the[BMP]Tf2N were studied by the means of cyclic voltammetry and chronoamperomety.The electrolyte of electrodeposition and cyclic voltammetry curves was tested at various temperature,scan rates and substrates.Electrodeposition was carried out using potentiostatic method.Deposits was observed and characterized by SEM,EDS,TEM and XPS.The results showed that electrochemical reduction behavior of Mo changed obviously when the temperature above 100?.Electrodeposition of molybdenum at different temperature on Pt substrate was studied.Deposits were insoluble cluster at 60? and 80?;Mo metal layer can get at 100? and 120?.This occurs because a low-price insoluble substance was produced and it hindered the reduction of the next step at low temperature.The metallic molybdenum can be obtained potentiostatially at-2.2V and-2.7V on platinum electrode at 120?.Deposit obtained at-2.2V was flat without cracked,while deposit obtained at-2.7V contained crystalline molybdenum though it was cracked.Compared with[BMP]Tf2N-MoCl5,cyclic voltammetry curve of[BMP]Tf2N-MoCl3 showed a straight line between 0V to-1.8V and there is only one reduction peak at-2.4V.This reason is that the reduction of Mo(0)occured between 0V to 1.8V.The results of potentiostatic deposition under different temperature and different potential showed that the plating cannot be obtained in[BMP]Tf2N-MoCl3.The CV curves of different scan rate shows that in[BMP]Tf2N-MoCl5 system,reduction peaks of R1 and R2 were an irreversible process of single electron and the charge transfer coefficient was about 0.18 at 120?.Chronoamperomety curve showed that reduction process of was Mo a quick charging for electric double layer and then followed by three dimensional continuous nucleation and three dimensional instantaneous nucleation.The study showed the plating obtained on Ni are loose and with poor adhesion.Compare to the Pt substrate,CV curve showed another a pair of REDOX peaks on Ag substrate,this was due to the different inhibition of absorption for different substrates.Electrodeposition of molybdenum on anodic dissolved Ag and mechanical polished Ag was studied.The result showed the plating was crystallized and crystal particle was observed on Ag after potentiostatic dissolution at 1.5V for 1.5 hours.The reason is that oxide can be removed on Ag after anodic dissolved,thus more active site exposed and then prompted atomic array regular and then crystalline was formed.